For a decade, it was known by its postal address – 1 Undershaft, a string of characters that told you where to find it and nothing about what it intended to become. In June 2026, the project received a name worthy of its ambition: One London. The rebranding, announced by developers Aroland Holdings and Stanhope alongside architect Eric Parry, marks the transition from planning argument to physical reality. Demolition of the 1960s St Helen’s Tower on the site is already underway. Main contractor appointment is expected later this year. Construction will begin in 2028, and by 2033, the City of London will have a new tallest building – one that matches The Shard, metre for metre, at 309.6 metres above ordnance datum.
The numbers alone are striking: 74 storeys, 154,156 square metres of Grade A office space, a cost exceeding £1 billion. But what makes One London genuinely significant is not its height. It is the argument the building forces London to have with itself – about heritage and commerce, and whether a skyscraper can do more than fill leasable floors.
The Long Road from Trellis to Tower
The site at the junction of Leadenhall Street and St Mary Axe has been contested ground since 2015, when Aroland Holdings – a consortium of Southeast Asian investors advised by Singapore-based Perennial Holdings – first engaged Eric Parry Architects to replace the 23-storey St Helen’s Building, a 1969 office block by Gollins Melvin Ward. That initial proposal, nicknamed “The Trellis” for its external cross-bracing, secured planning consent in 2016. A revised scheme followed in 2019. Neither proceeded to construction.
In August 2023, Parry unveiled a substantially different design. The single tapered volume was replaced by a quad-segmented tower – three stacked blocks with terraces, rising to 309.6m AOD, the exact height of Renzo Piano’s Shard. The revision increased usable floor area by roughly 30 per cent and was driven, Parry told the Architects’ Journal, by changes to working habits after the pandemic: “the ways that we use buildings have evolved significantly.” The redesign also responded to the City of London Corporation’s City Plan 2040, which identifies a minimum of 1.2 million square metres of net additional office space as the City’s requirement over the next 16 years. One London alone will deliver nearly 13 per cent of that target.
The City of London Corporation’s Planning Applications Sub-Committee voted to approve the revised scheme on 13 December 2024, by 16 votes to seven, with two abstentions. Full planning consent followed in December 2025. The project has now moved from debate to deconstruction: Keltbray is dismantling St Helen’s Tower, which at 118 metres will be the largest skyscraper ever demolished in London.
What the Building Actually Contains
One London’s programme is more layered than the headline floor count suggests. The lower eleven storeys form a podium topped by a 2,500-square-metre public garden, designed with landscape architects SLA, offering a 330-metre perimeter walk with views of St Paul’s Cathedral, the Lloyds building, and 30 St Mary Axe – the Gherkin. Above that, the tower’s bulk is dedicated to commercial workspace designed to accommodate between 7,000 and 10,000 occupants.
The uppermost two floors – levels 72 and 73 – are where the building’s civic ambition is most visible. Level 73 will house Europe’s highest publicly accessible viewing gallery, operated by the London Museum. Level 72 will contain educational “classrooms in the sky,” designed to give schoolchildren and community groups the chance to study London’s geography and history from over 300 metres. The spaces will be free to access and open seven days a week, including evenings.
At ground level, the project will transform the public realm from St Mary Axe to parts of Leadenhall Street into a step-free pedestrian zone with new greening, seating, wayfinding, and a large digital screen for public events and screenings. A food and beverage offer on the 10th floor will sit below the garden.
Eric Parry described the design philosophy to Wallpaper* in June 2026: “There was a realisation that there’s a massive problem with supply of office space in the City. There was a need for space, but also for breathing space, for access to air and the environment, to get away from the sealed box, which gave rise to this idea of a building that works on multiple horizons in a way that really is beneficial to the wellness of the occupant.” He added: “I had a vision for the top of the building to be civic rather than commercial.”
The Heritage Battle That Refuses to Settle
No aspect of One London has proved more contentious than its impact on the surrounding historic environment. The site sits within a dense concentration of heritage assets: the medieval church of St Andrew Undershaft, the Grade I-listed Lloyds building by Richard Rogers, and the Tower of London World Heritage Site, all within close proximity.
Historic England, the government’s statutory heritage adviser, has opposed the revised scheme throughout. In an objection letter in May 2024, the body warned that the redesigned podium and 11th-floor garden platform, cantilevered 42 metres above street level, would “fundamentally compromise” the character of St Helen’s Square and “seriously degrade the scale and character of the public realm around it.” The heritage watchdog described the revised plans as “arguably worse” than the previously consented Trellis design and recommended refusal.
Following the December 2024 approval, a Historic England spokesperson said: “We are disappointed that this scheme has been approved because the people of London deserve better. The proposed building will have a harmful impact on precious public space, as well as on the important listed buildings beside the development site and the Tower of London World Heritage Site.”
The objections were not limited to heritage bodies. Bruce Carnegie-Brown, then chairman of Lloyd’s of London, wrote to the City Corporation urging rejection “as currently presented,” arguing the scheme would “rob the City of a really important convening space.” The Universities Superannuation Scheme, a £90bn pension fund and neighbouring occupier, maintained its objection through the final vote, citing concerns about the digital screen’s security implications and the loss of ground-level public space. Tower Hamlets Council also opposed the scheme over its projected impact on the Tower of London.
Planning officers recommended approval regardless, arguing the public benefits – the office supply, the London Museum education spaces, the improved pedestrian realm – outweighed the heritage harm. The committee agreed, though seven members voted against, a notable level of opposition for a scheme that had been through multiple design iterations.
Eric Parry and the Question of Civic Architecture
The architect behind One London is not, by temperament, a builder of icons. Eric Parry, born in Kuwait in 1952, founded Eric Parry Architects in 1983 and has spent four decades producing work characterised by material sensitivity and contextual restraint rather than spectacle. His best-known projects include the restoration of St Martin-in-the-Fields in Trafalgar Square, the Holburne Museum extension in Bath, and 30 Finsbury Square. He was elected Royal Academician in 2006 and awarded a CBE.
One London is the most prominent project of Parry’s career. “Tall buildings can generate huge amounts of value in our cities,” he said when planning consent was granted in December 2024. “1 Undershaft is a generous building with the aspirations to be a next generation classic of its kind, both for the public and occupants.”
The building’s structural expression reflects this ethos. Its ground-floor columns, which Parry calls “giant redwoods,” are made of weathering steel and designed to branch as they rise, supporting the garden platform while continuing to the full 300-metre height. The tower’s white vitreous enamel cladding was chosen for longevity: “There are very few buildings over 200m that are ever pulled down, so there’s a responsibility,” Parry told Wallpaper*. “This is going to be there, perhaps, as long as the Tower of London.”
Sustainability and the Problem of Permanence
One London’s sustainability claims are extensive, though partly unquantified. The team is exploring both BREEAM and NABERS UK rating frameworks. The landscape strategy, developed with SLA, claims a 960 per cent Biodiversity Net Gain over the existing site, including a nearly five-fold increase in urban greening. Hanging gardens at each terrace setback and the 11th-floor podium garden will function as biodiverse habitats at an elevation rarely attempted in London.
The facade is designed for passive environmental performance. Parry has been explicit about rejecting the all-glass curtain wall: “I didn’t want to make another building all in glass with a closed cavity system with blinds that come down. We wanted it to be passive, with shading.” Whether One London delivers on these ambitions will depend on fit-out and operational management – areas yet to be specified. But the ambition to design a tall building for a century-long lifespan, rather than a 30-year depreciation cycle, is itself a statement about how London’s relationship with height might evolve.
What One London Means for the City’s Skyline
When One London is completed in 2033, it will stand as joint tallest building in Western Europe with The Shard, though the two will never be seen as equals. The Shard sits on the South Bank, surrounded by open ground along the Thames. One London will be embedded in the Eastern City Cluster, squeezed between Foster’s Gherkin at 180 metres and RSHP’s Leadenhall Building at 224 metres. Its visual impact will be less about individual grandeur than about collective mass – the City’s cluster becoming, definitively, a wall of towers.
The question One London forces is whether the cluster model – buildings packed tight, competing for light and sky – is the right way for a historic city to grow. Parry thinks so: “It’s a very English one, this sense of a cluster of buildings that relate to a landscape idea, placed as sort of foothills.” Whether you see One London as a civic gift or a corporate intrusion will depend on how much you trust a 300-metre tower to honour its promises – free public education spaces, open gardens, a genuinely accessible ground plane – once the tenants move in and the security apparatus settles. The heritage objectors were not wrong to worry. The planning officers were not wrong to weigh the benefits. The building will be both, and London will argue about it for as long as it stands.
