The Fifth Desk · Evaluation
Act I · The Map
Norman Foster (Foster and Partners) · an office tower built as the headquarters of a reinsurer, scored as the tower as it stands: the one tower with its diagrid, its glazed skin, its spiralling lightwells, its office floors, the domed room under the lens at its top, its ground-floor lobby and the open plaza round its foot · forty-one storeys and 180 metres, circular in plan at every level, swelling from the base to its widest girth about a third of the way up and tapering to a glazed lens · a perimeter diagrid of steel members meeting at nodes, carrying gravity and wind together, round a central steel core, the floors spanning between core and diagrid; each floor cut at its edge by six triangular lightwells and turned against the floor below, so that the lightwells spiral up the tower and read outside as dark helical bands; a double-glazed skin of flat panes · in St Mary Axe, City of London, on the site of the Baltic Exchange, wrecked by the IRA bomb of 10 April 1992 and later demolished · completed 2003, opened 2004; RIBA Stirling Prize 2004 · Norman Foster, Foster and Partners, for Swiss Re as owner-occupier; Arup, structural engineers; Skanska, main contractor · as it stands, whole in its fabric; sold by Swiss Re in 2007, in receivership in 2014 and bought by the Safra Group the same year, and now let to many tenants
Mode
An office tower as a single figure; a round, tapering tower of steel diagrid and flat glass, the lightwells spiralling up its floors, on an open plaza
Mythos
The spiral of growth by rotation, the form of shell and pine cone, built into the section and visible on the skin; the tower closing to a lens, an eye on the sky, half built; the egg, the bullet and the pickle supplied by the city, not by the building
Phase
The Baltic Exchange wrecked by the IRA bomb of 10 April 1992 and later demolished; a taller Foster scheme for the site, the Millennium Tower for Kvaerner, not built; completed 2003, opened 2004; the Stirling Prize 2004; sold by Swiss Re in 2007, in receivership and bought by the Safra Group in 2014; let to many tenants since
Presentation
Forty-one storeys and 180 metres; a circular plan swelling and tapering in section; a perimeter diagrid round a central core; six triangular lightwells to each floor, each floor turned against the last; a double-glazed skin of flat panes; a domed room under the lens; a low lobby; an open plaza round the foot
Register
Buoyant, serene and exhilarating, never terrible; the confidence of a financial city round the year 2000
Scale
One tower in the old financial core; finance and insurance, the city as skyline, plaza and district, and air and light as programme
Governing Proposition
On a site emptied by a bomb, a reinsurer asked the City of London for a headquarters, and was given a figure instead of a block: a round tower whose structure is its pattern, whose dark spirals are its lightwells, and whose foot is handed back to the street as a plaza. The wager of the building is that one rule, the circle turned floor by floor inside a diagonal grid, can govern a tower from the steel node to the whole figure. The rule holds. What it governs is an office building, and most of what the form promises for the life inside it is a promise.
Act II · The Essay
Movement I
On 10 April 1992 an IRA bomb exploded in St Mary Axe, in the City of London, and wrecked the Baltic Exchange, which stood there. The Exchange was later demolished. The site at the heart of the old financial core stood empty, and what would be built on it was a question about the City as much as about one plot.
Foster drew for the site in the 1990s a scheme of another order, the Millennium Tower for Kvaerner, far taller than anything the City allowed, and it was not built. The City had long kept its towers few, under a skyline policy that guarded the views of St Paul’s. The building that stands there now came from a second client and a second design: a headquarters for Swiss Re, the reinsurer, which was to occupy it itself. It was completed in 2003 and opened in 2004.
The commission inherited the London office block and the extruded glass tower of the 1960s to the 1990s, rectangular in plan and in section, each floor like the last. It brought, from Foster’s own work, a line of argument about towers and air: the Climatroffice, drawn with Buckminster Fuller in the early 1970s, and the Commerzbank at Frankfurt, of 1997, with its spiralling gardens and floors meant to be ventilated naturally. Arup were the structural engineers and Skanska the main contractor. Collaboration is not charged; the design is Foster’s, with Foster and Partners.
Movement II
The tower is circular in plan at every level. In section it swells from a narrow foot to its widest girth about a third of the way up, then tapers to a glazed lens at the top, forty-one storeys and 180 metres above the street. It stands back from the street on an open plaza, on a small footprint for its floor area, and the ground the circle frees is given back to the City as public space.
The structure is at the surface. A perimeter diagrid of steel members, meeting at nodes, carries gravity and wind together; a central steel core rises inside it; the floors span between core and diagrid, free of perimeter columns. The diagonal grid that holds the tower up is also the pattern the eye reads on it. There is nothing applied to remove: the structure is the ornament, the taper is the profile. The round body leads the wind round the tower instead of down it into the lanes, and from those lanes it shows less bulk than a block of the same floor area would.
The curve was made from straight things. The skin is double-glazed in flat panes, set in the diagrid’s triangles, so that a doubly curved body is built of flat glass and straight steel, by modelling that fixed every node and every pane. That is the tower’s command as a made thing: one system doing structure, enclosure and figure at once. The argument for the round form is weaker than the form. The curve came first and the wind second, and curved floor plates fight the desks and partitions an office needs.
Movement III
Each floor plate is cut at its edge by six triangular lightwells, and each floor is turned against the floor below, so that the lightwells rise through the tower in spirals. Outside they read as dark helical bands winding round the body. The pattern on the skin is the section of the building: the bands are the voids inside, seen from the street. The spiral, growth by rotation, the form of shell and pine cone, is here not an image but a construction, and it bears load in the plan of every floor.
The lightwells were argued as the tower’s environmental machine: to bring daylight deep into the plan and to drive natural ventilation, with energy use claimed at about half that of a comparable tower. That claim was made from the start and is part of what the building put in the open. How far natural ventilation is used in practice is disputed, and the performance in use has not been shown. The form is compelled by a logic its use may not keep.
Inside, the voids join floors into tall, stepped spaces, so that people on one floor see others above and below them, and light reaches further into a round plan than into a deep box. Otherwise office work is lived much as in any tower of its date, on floors round a core. Since Swiss Re sold the tower in 2007 it has been let to many tenants, and their fit-outs cut the spiralling voids into separate rooms. The rule that governs the figure from outside bends to the leased floor within.
Movement IV
At the top the diagrid closes to a point under a glazed lens, and beneath it is a domed room, a bar and restaurant, with London on every side and the steel converging overhead. It is one of the great rooms of its kind, and the third place where the building’s height is felt, after the plaza, where the lattice swells overhead and curves away, and the City at large, where the tower stands as a single dark figure among blocks with its spirals turning as one walks. For most of the building’s life the room has been a private one, reached by few.
The tower closing to a lens is the second pattern the building half builds: an eye on the sky, a dome of the heavens set on a counting-house. It stays half built because nothing in the plan leads to it. There is no threshold, no axis and no procession; the lobby at the foot is modest and low, closed to the plaza more than open to it; and the lift takes the visitor up. The ascent the figure promises is a ride.
The city supplied the rest of its myths. The egg, the bullet and the pickle are its jokes, not the building’s construction, and the nickname by which most people know the tower is a domestication of it rather than an archetype. The register the building itself holds is serene and exhilarating, never terrible: the buoyant confidence of a financial city in the years round 2000, made into one shape on its sky.
Movement V
The tower was the first tall building in the City for a generation, and it drew ridicule before it drew affection. It won the RIBA Stirling Prize in 2004. Its departure was a round, tapering tower of curved diagrid in the old financial core, with no flat front; the turn had been prepared at Frankfurt and in the Climatroffice, and Jean Nouvel’s Torre Agbar was rising at Barcelona at the same time. The reach that followed is wide and specific. The City opened to tall buildings, and the cluster that grew round the tower took its terms, each new tower given a figure and a nickname; the diagrid became a standard option for towers, Foster’s own Hearst Tower, of 2006, among the first.
The building was made for one owner and has outlived that purpose. Swiss Re sold it in 2007; it went into receivership in 2014 and was bought by the Safra Group the same year. Its use continues without a break, as offices, but changed in kind, from one company’s headquarters to an asset let to many. The image never changed. The diagrid, the skin, the spirals, the lens and the plaza stand as built, and the figure is the emblem of the City in images of London.
Lloyd’s, by Richard Rogers, stands a few streets away and turned its building inside out to change how its great room is used; this tower made a figure. Its strength is in its law: the circle, the curve, the diagonal grid and the rotation, governing everything from the steel node to the lens. Its limit is in what that law governs, an office building whose interior lives as offices do, a record of twenty-three years, and a surface that belongs to a moment of taste and technology not yet outlived.
Act III · The Twelve
Judged on purpose, structure and site, more of this tower passes the subtractive test than most towers do. There is no ornament to remove: the diagrid is the structure and the pattern, the dark spirals are the lightwells, the taper is the profile. The circular plan and the swelling-and-tapering section were argued from the site: a smaller footprint for the floor area, a plaza returned to the street, wind led round the tower instead of down it, less bulk seen from the lanes of the City. The argument is weaker than the form. The lightwells and the rotation were drawn for a ventilation scheme whose use is disputed; the curve was chosen first and justified by wind second; and curved floor plates fight the office fit-out.
Score: 8.0 / 10
What the building brings into the open can be stated, and it holds. On a site made empty by a bomb, the finance of the City answered with a figure rather than a block: a private tower that gives its foot back to the public as a plaza and presents itself as an environmental machine. It disclosed that a corporate office tower could be one legible object, known by a nickname, and that its making could be claimed as care for air and light. What holds the axis: much of this is a statement about architecture and corporate image, not about a way of living; the environmental claim it puts in the open is one its use has not been shown to keep; and what it gives the city is chiefly a mood.
Score: 7.5 / 10
Elevation is real and comes in three places. From the plaza the diagrid swells overhead and curves away, a lattice that seems to breathe outward and then close. Across the City the tower is a single dark figure among blocks, its spirals turning as one moves. At the top, in the domed room under the lens, London lies on every side and the steel closes to a point overhead: one of the great rooms of its kind. Frequency is lower. The lobby is modest and low; the office floors are offices, their spiralling voids giving a glimpse of floors above and below, not a nave; and the top room has been a private one for most of the building’s life. The register is serene and exhilarating, never terrible.
Score: 8.1 / 10
One pattern is built, not alluded to: the spiral. The lightwells turn up the tower floor by floor, so that growth by rotation, the form of shell and pine cone, bears load in the section and is visible on the skin. A second is half built: the tower closing to a lens, an eye on the sky, the summit room a dome of the heavens set on a counting-house. The rest is projected. The egg, the bullet and the pickle are the city’s jokes, not the building’s construction, and the nickname most people know is a domestication, not an archetype. What holds the axis below the Universal Minimum: no threshold, axis or procession gives the visitor an ascent. The lift takes them up.
Score: 7.4 / 10
The inheritance: the London office block and the extruded glass tower of the 1960s to the 1990s, rectangular in plan and section, and in the City a skyline policy that guarded St Paul’s and kept towers few. The departure: a round, tapering tower of curved diagrid in the old financial core, with no flat front and no upper floor like the lower ones, its environmental scheme the stated reason for its form. The stake was real: the first tall building in the City for a generation, on a contested site, and a form that drew ridicule before affection. What holds the axis: the turn was prepared in Foster’s own work, the Climatroffice of the early 1970s and the Commerzbank at Frankfurt of 1997, and Torre Agbar was rising at Barcelona at the same time.
Score: 8.1 / 10
Would a different form change what the tower knows? Outside, entirely: put the floor area in a box and the plaza, the wind led round the body, the slender figure seen down the lanes and the sign on the sky are all gone. Inside, in part. The spiralling lightwells join floors into tall, stepped voids, so that people on one floor see others above and below, and daylight reaches deeper into a round plan than into a deep box; the domed top makes the summit a room, not a plant floor. But office work inside is lived largely as in any tower of its date, on floors round a core, and multi-tenancy since 2007 has partitioned what was planned for one owner’s staff. Form as instrument of the figure and the light.
Score: 7.8 / 10
Evidence over promise, over twenty-three years. The tower has yielded to the study of computational design, as a case of parametric modelling carried through structure and skin; to engineering, as the diagrid tower most cited; to environmental design, in the open argument whether its claims were met; to planning, as the building that broke the City’s resistance to towers and began its cluster; and to the culture of the icon, the nicknamed tower made emblem of a city’s finance. What holds the axis below the Universal Minimum: the questions stay open, but they concern its making, its reception and its city more than what its form means. Once seen, the figure gives the same thing on return, the interior gives less, and the record is short.
Score: 7.4 / 10
Standing since 2003, it is scored on force and reach together, in the field of the tall office building and of London architecture of its decades. The intrinsic force: the tower made a curved diagrid buildable at height from flat panes and straight members, joined structure, skin and form in one system, and made environmental performance the stated argument of a tower’s shape; but the green tower was Foster’s at Frankfurt first, and the diagrid was not new. Achieved reach is scored with intrinsic force: wide and specific. It opened the City to tall buildings and set the terms of the cluster that followed, each tower given a figure and a nickname; it made the diagrid a standard option for towers, Foster’s Hearst Tower of 2006 among the first; and it fixed the shaped, named tower as the emblem of a financial district.
Score: 8.2 / 10
Weighed on form, then use, then fabric, over twenty-three years. The form survives whole: diagrid, skin, spirals, lens and plaza are as built, and the figure has outlived the boom and the client that made it, now the emblem of the City in images of London. The use survives, changed in kind: offices without a break, but no longer one owner’s headquarters, sold, fallen into receivership and bought again within eleven years, and the top room private for most of its life. The fabric has held. Presence is very wide and earns at most a tenth. What holds the axis is age: the survival shown is short, and the surface belongs to a moment of taste and technology not yet outlived.
Score: 8.2 / 10
Judged as command of building, structure and engineering included. The command is of the first rank and bears load. The diagrid carries gravity and wind together at the perimeter, freeing the floors of perimeter columns. A doubly curved surface is built from flat glass and straight steel, by modelling that fixed every node and pane. The rotation of the floors, the triangular lightwells and the diagonal grid were made to agree exactly, so that the spiral reads clean on the skin; the lens room is a dome of steel and glass closing to a point. The costs: the base meets the plaza with a low, closed lobby less surely than the tower meets the sky, and the environmental system is a making whose performance in use is disputed.
Score: 8.7 / 10
Take the two most distant elements: the plaza at the foot, stone and air, and the lens at the top, a glass dome closing to a point. One law governs both: the circle in plan, the curve in section, the diagonal grid on the surface, and rotation from floor to floor. The plaza is the space the circle frees from the site; the lens is where the curve and the grid meet at a point; the dark spirals between are the same rotation made visible. The law holds from the steel node to the whole figure and from inside to out, a wide range for one rule. What bends it: the office floors answer to the core and the leased floor, so fit-outs cut the spiral voids into tenants’ rooms, and the lobby belongs to a plainer law.
Score: 8.5 / 10
Orders held: finance and insurance, which commissioned the tower and now trade it; the city, as skyline, plaza and the planning of a district; the natural order, in wind, light and air built into the plan and section, more as programme than as presence; and history, faintly, in the bomb site, which the form does not take up. The section integrates the first three: the plaza, the spirals and the figure on the sky place commerce in the air and light of the city, so they are joined, not listed. What holds the axis lowest of the twelve is what is absent: the household, labour beyond the office, the state, the sacred, death and the body. An office tower holds a financial city’s confidence at one moment, and the figure describes the form.
Score: 6.8 / 10
Act IV · The Reckoning
7.9 / 10 · Final Average
Placement: Tier III · Major
Strongest Dimensions
The Made at 8.7, then The Inner Law at 8.5, then Pressure on Tradition and The Imperishable at 8.2. A curved tower built from flat glass and straight steel, its diagrid carrying gravity and wind together and its floors, lightwells and grid made to agree so that the spiral reads clean on the skin; one law, the circle turned floor by floor inside a diagonal grid, running from the plaza at the foot to the lens at the top; a figure that opened the City to tall buildings and made the diagrid a standard option for towers; and a form standing whole after twenty-three years.
Limiting Dimension
The Encompassed at 6.8: finance, the city and air and light as programme are held, with the household, labour beyond the office, the state, the sacred and the body absent. Then The Archetypal Deep and The Bottomless Well at 7.4: one archetype built, the spiral, with no threshold or ascent to live it, the lift doing the climbing; and a short record whose questions concern the tower’s making and its city more than what its form means. Then The Unconcealment at 7.5: the disclosure of an aspiration and a mood, its environmental claim one its use has not been shown to keep. These hold the work below Tier IV, and they are one fact: the law that makes the figure governs an office building, and what the form promises for the life inside it is mostly promise. Lloyd’s Building (8.0), a few streets away in the City, stands a tenth above, higher on seven axes, by most on The Living Form, because it changed how its room is used where this tower made a figure. The Chrysler Building (8.1) stands above it, chiefly on The Imperishable, for a survival of nearly a century. CCTV Headquarters (7.9) stands level with it; Walt Disney Concert Hall (7.8), of the same age, and the Burj Khalifa (7.8) stand a tenth below.
The Necessity Cap clears at 8.0 against a threshold of 7.5, by five tenths. The Coherence Floor clears: The Living Form at 7.8, The Made at 8.7, The Inner Law at 8.5, each against 7.0. The Epochal Gate is unmet on all five: Pressure on Tradition at 8.2 and The Imperishable at 8.2 fall three tenths short of the bar of 8.5, The Swerve at 8.1 four tenths short, The Unconcealment at 7.5 a point short and The Archetypal Deep at 7.4 a point and a tenth short. The Universal Minimum is unmet at The Archetypal Deep, 7.4, and The Bottomless Well, 7.4, both below 7.5; The Encompassed, which it exempts, clears its own floor of 6.0 at 6.8. Three of the five summit conditions are met. The work stands where its aggregate places it: 7.9, from a sum of 94.7, in the band of Tier III, a tenth short of the 8.0 at which Tier IV begins and short of the 9.0 that the summit requires.
Basis · a reading from knowledge of the tower as it stands in 2026 and of its documented form, structure, history and reception; the knowledge is good for form, structure, history and reception and thinner for the interior as fitted and for environmental performance in use. No plan, image or written source was consulted. The unit scored is the tower as it stands: 30 St Mary Axe, the one tower of forty-one storeys, with its diagrid, its glazed skin, its spiralling lightwells, its office floors, the domed room under the lens at its top, its ground-floor lobby and the open plaza round its foot. The Baltic Exchange that stood on the site, the Millennium Tower that Foster drew for the site for Kvaerner in the 1990s, and the later towers of the City cluster round it are context only and are not scored. Nothing of the tower is recorded here as lost, replaced or rebuilt: it stands where the Baltic Exchange stood, and as built, with tenants’ fit-outs dividing the office floors since 2007; the change from one owner’s headquarters to a building let to many is weighed under The Imperishable and under The Living Form. The design is Norman Foster’s, with Foster and Partners, for Swiss Re; Arup were the structural engineers and Skanska the main contractor; collaboration is not charged, and the other members of the office’s team are not named. Nothing is quoted: no inscription or documented statement on the building is held word for word. The nicknames are named as the city’s readings and are not credited. The energy figure is given as the claim that was made; how far natural ventilation is used in practice is disputed, and the page does not settle it. Facts that could not be verified are not given, among them the height of the Millennium Tower scheme, the date of planning consent and of the start of building, the month of opening, the dimensions and level of the widest girth, the angle by which each floor is turned, the area of glazing, whether the lens is the only curved glass, the later uses of the top room, the prices of the sales, an early fault in the glazing, and a Roman burial reported from the site.