1 Undershaft

1 Undershaft is a supertall skyscraper planned for the City of London financial district. The scheme is being developed by Aroland Holdings and designed by Eric Parry Architects. It is set to replace the St Helen's tower, and if built will share The Shard's status as the tallest skyscrapers in London and the United Kingdom.

The building is the third design for a skyscraper at 1 Undershaft, replacing two previous proposals designed by architects Avery Associates and Eric Parry themselves respectively. The second proposal, nicknamed 'The Trellis ' due to its external cross bracing, was given approval in November 2016, but this design was ultimately discarded in favour of a quad-segmented tower revealed in August 2023.

The substantial changes entailed will result in 1 Undershaft needing to once again apply for planning permission from the City of London Corporation. Construction is planned to take around five years subject to planning, with enabling works starting in 2024, construction work starting in late 2025 after the demolition of St Helen's tower, and completion in 2029.

Original proposal (early 2015)
In January 2015, early plans emerged of a replacement office building for the St Helen's tower in Undershaft within London's Square Mile. The proposal, named 1 Undershaft, was designed by Avery Associates; who began working on the scheme in collaboration with the then-owner of the site, Simon Halabi, in 2010. At 270 m, it would have become the third-tallest building in London and the United Kingdom, behind The Shard and 22 Bishopsgate.

Second proposal (late 2015)
In July 2015, details of a revised scheme by the new owners of the site, Aroland Holdings, were reported. The plans were for a skyscraper of 304 m designed by Eric Parry Architects. According to some reports, the design could be "modelled on Cleopatra's Needle".

In December 2015, the new design was released for a tower of 294.6 m with 73 floors. Subject to planning permission, it was set to become the tallest building in the Square Mile when completed and the second-tallest building in London and the United Kingdom, behind The Shard. A consultation process took place in autumn 2015. On 8 February 2016, a planning application was submitted for the development, with a decision expected to be made in September 2016.

However, a revised planning application was submitted by the developer which reduced the proposed height by 4.66 m to 289.9 m, due to possible interference with the flight paths of the nearby London City Airport. Each floor was reduced in height by 50 mm and structural floor beam depths were changed. In addition, the level of the soffit was decreased and the viewing gallery height reduced, which was intended to be double height. Despite its height reduction, the proposed height will still make 1 Undershaft the second-tallest building in London and the United Kingdom upon completion.

Following a recommendation by planning officers for approval, the scheme was approved by the City of London Corporation on 28 November 2016, with 19 votes in support and two against; final approval was given by Mayor of London Sadiq Khan on 12 December 2016. The start date for construction of the scheme has not yet been decided, but building work is expected to be finished anywhere between six and 10 years from its approval date, with demolition of the St Helen's building currently on the site expected to take 18 months and construction of 1 Undershaft due to take between three and four years.

Design
The second design's proposed skyscraper is rectangular in shape and slightly tapers as it gets higher. Developer Aroland Holdings, a British Virgin Islands entity of undisclosed ultimate ownership, originally wanted 1 Undershaft to be taller than the proposed height. However, the height has been limited by the Civil Aviation Authority (CAA) to avoid intruding on flight paths. In addition, the building's crown, which was intended to resemble Cleopatra's Needle, was not accepted by City planners who wanted "a less demonstrative top. They didn't want another overt shape".

The tower is designed to be built 10.5 m off the ground in order to create public space underneath the building. To make room for the public space, the core will need to be positioned to the side of the tower. As a result, bronze-coloured diamond-shaped external cross-bracing will be required, giving the building its nickname The Trellis.

A public square is also part of the proposed scheme, with 2178 m2 of retail space below ground level. The top of the skyscraper is set to have London's highest viewing gallery free for public access (which could include a museum run by the Museum of London), and a restaurant.

Construction financing scam
In 2017, a bogus bond financing scheme supposedly funding the construction of 1 Undershaft was launched in the United Kingdom. A £30 million tranche of 9-year bonds was issued by Trade Mark International Limited, a Cayman Islands-registered limited company. An accompanying website, www.trademarktint.com, was registered by Paul Mantoura.

A number of investors subscribed for the bonds, yielding 10% per annum coupons and a capital guarantee at maturity, through Paul Mantoura and his Platinum Associates firm in Brazil. However, when investors stopped receiving communications in 2020, Intel Suisse, a financial investigation specialist firm, was called in and discovered the fraud: Trade Mark International never existed. The webhost firm confirmed Paul Mantoura's ownership of the website, which he acquired in 2017 and is now offline.

Third proposal (2023)
In August 2023, Eric Parry Architects revealed a substantially revised design for 1 Undershaft, prompted by changes to working habits following the COVID-19 pandemic, as well as to improve the building's sustainability credentials. In place of the previous cross-braced and tapered tower, this redesign proposes a tower segmented into four vertical blocks, increasing the usable floor area by 30%. At 309.6 m (AOD), the revised configuration will reach the exact same height as The Shard, sharing its status as the United Kingdom's tallest buildings.

A public roof garden on the 10th floor has been added, extending over a curved canopy above the corner of Leadenhall Street and St Mary Axe; several winter gardens up to approximately 1,530 m2, external office terrace spaces up to 1,370 m2, and around 110,000 m2 of workspace, up from the second design's 90,000 m2. The public viewing gallery, shared with the Museum of London, remains part of the proposals.