One London (formerly known as 1 Undershaft) is a 74-storey, 309.6-metre commercial tower planned at the junction of Leadenhall Street and St Mary Axe, at the heart of the City of London's Eastern City Cluster, breaking ground in 2028 and set to finish in 2033.
Designed by Eric Parry Architects for Aroland Holdings, with Stanhope as development manager, the tower replaces the 1969 St Helen's Tower and will match the height of the Shard as the capital's joint tallest building. Around 1.2 million square feet of workplace serves between 7,000 and 10,000 workers, while the top of the building is given over to civic uses, including Europe's highest publicly accessible viewing gallery and London Museum education spaces where school children and young people can experience London from on high. The 11th floor carries a public garden integrated into the building's structural language: a forest of weathering steel pillars that Parry calls 'giant redwoods', branching to support the garden while continuing up to carry the tower above. The scheme targets BREEAM and NABERS UK ratings, and its landscape strategy by SLA promises a 960% biodiversity net gain across the site. The white, passively shaded facade trades the typical sealed glass tower for a more open, vertically gardened expression.
Keltbray has spent more than a year stripping out and demolishing the 1969 St Helen's Tower on the site, with the main contractor appointment for the £1bn-plus tower due in 2026 and bidders expected to include Mace, Multiplex and Bovis.
bdonline.co.ukThe former 1 Undershaft was unveiled as One London, with construction set to start in 2028 and finish in 2033.
constructionenquirer.comDismantling of the existing St Helen's Tower has begun on the site, clearing the way for a 2028 construction start on the 74-storey, 309.6-metre Square Mile tallest.
constructionenquirer.comEric Parry's revised 74-storey 1 Undershaft scheme approved by City of London planning sub-committee.
architectsjournal.co.ukThe outlook for One London
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Frequently asked
Where is One London located?
One London is located in London.
When will One London be built?
One London is an announced development that has not yet started construction, targeting completion in 2033.
Who is developing One London?
Aroland Holdings, Stanhope is the developer behind One London.
Who designed One London?
One London was designed by Eric Parry Architects.
How big is One London?
One London rises 74 stories.