Plans Unveiled for West Europe’s Joint-Tallest Tower: London 2026

Key Points

• Record-Breaking Dimensions: The newly unveiled skyscraper, designated as One London (historically known as 1 Undershaft), will stand at a staggering height of 309.6 metres (1,015.75 feet) Above Ordnance Datum (AOD). This height precisely matches The Shard, making it the joint-tallest building in Western Europe and the outright tallest tower within the City of London financial district.
• Corporate Backing and Timeline: The landmark commercial project is being brought forward by developer Aroland Holdings, who are advised by Perennial Holdings, alongside development managers Stanhope. Designed by the acclaimed Eric Parry Architects, the tower has received formal planning clearance and is scheduled for structural completion by 2033.
• Massive Commercial Capacity: The 74-storey development will inject approximately 154,156 square metres of Grade-A office space into the Square Mile. This massive volume is projected to single-handedly satisfy nearly 13% of the City of London’s total commercial space requirement under the comprehensive City Plan 2040 framework.
• Public Infrastructure and Culture: The architectural plans incorporate Europe’s highest free-to-visit public viewing gallery and a dedicated children’s educational space at levels 72 and 73, curated in partnership with the London Museum. It will also feature a 2,500-square-metre public podium garden on the 11th floor and a massive 12.5-by-7-metre digital entertainment screen facing St Helen’s Square at its base.
• Design Transformation: Moving away from its initial cross-braced “Trellis” aesthetic approved in 2016, the modern configuration features a quad-segmented vertical block design. This updated structural layout yields a 30% increase in total internal floor area while achieving a 500% increase in localized Biodiversity Net Gain through extensive biophilic engineering.

London (The Londoner News) June 1, 2026 – A consortium of global real estate developers and architects have officially pulled back the curtain on “One London,” an ambitious 74-storey commercial skyscraper slated to redefine the United Kingdom’s capital skyline by becoming the joint-tallest structural asset in Western Europe. Designed by Eric Parry Architects on behalf of primary developer Aroland Holdings — and strategically advised by Perennial Holdings alongside development giants Stanhope — the mega-structure will scale to an absolute height of 309.6 metres. This exact altitude matches Southwark’s iconic Shard tower, positioning One London as the tallest office building and the undisputed architectural apex of the City of London’s eastern financial cluster upon its projected completion in 2033.

The structural blueprint, which marks the culmination of a decade-long planning cycle and multiple radical design overhauls, replaces the existing 28-storey Aviva Tower at St Helen’s. Beyond its primary role as a dense commercial hub, the project has been engineered to serve as a major civic asset. The developers have committed to delivering extensive public realms, including a multi-tiered public garden 42 metres above street level, an expansive ground-level public square, and an interactive educational academy operated concurrently with the London Museum. Local planning administrators have hailed the scheme as a monumental victory for London’s post-pandemic economic strategy, ensuring the metropolis retains its competitive edge against rival European financial centres.

What are the Architectural and Structural Dimensions of One London?

The physical scale of One London represents the absolute upper limit of architectural potential within the Square Mile, dictate entirely by regulatory restrictions. According to official project specifications published by Eric Parry Architects, the tower will reach 309.6 metres AOD. This precise ceiling is not arbitrary; it represents the maximum altitude permitted by aviation safety regulations enforced by the Civil Aviation Authority and London City Airport, which sits just a few miles to the east.

In a technical design statement released by the practice, Principal and Founder Eric Parry commented that

“The building is modelled to provide a series of urban horizons; street level, elevated public garden, amenity floors, and the London Museum classrooms and viewing gallery at the apex of the building.”

The structural layout deviates from traditional singular monoliths, instead adopting a “quad-segmented” profile consisting of three distinct stacked blocks interspersed with open-air terraces. This clever segmenting increases the total interior usable floor area by 30% compared to the earlier versions of the plan.

How Will the Development Impact London’s Commercial Office Market?

The introduction of One London comes at a time when the City of London Corporation is actively pushing to modernise its real estate stock to meet evolving corporate environmental demands. As detailed in the City Plan 2040 framework, the municipal government has identified a strict demand for a minimum of 1.2 million square metres of net additional office space over the next 16 years to sustain economic growth trends.

Upon its formal launch, One London will single-handedly provide 154,156 square metres of premium Grade-A workspace. This represents roughly 13% of the entire capital requirement for the City of London up to 2040. The development is specifically targeted at multinational institutions requiring massive, highly efficient floorplates that incorporate modern sustainability metrics.

In a public briefing following the approval of the plans, Shravan Joshi, Chairman of the City of London Corporation’s Planning and Transportation Committee, stated that

“1 Undershaft is a truly remarkable building that will not only help to deliver on the demands for economic growth, through the high-quality office space it offers, but also contribute to the City’s growing cultural offer and tourist appeal.”

What Public Amenities and Cultural Spaces are Included in the Design?

One of the most legally contentious and heavily scrutinized elements of the One London application was its civic contribution. To win over municipal planners, the developers revised the base and apex of the tower to create public infrastructure that aligns with the city’s ongoing “Destination City” campaign, an initiative aimed at transforming the financial district into a seven-day-a-week leisure destination.

The Apex: Europe’s Highest Viewing Gallery

At the very top of the 74-storey structure, across levels 72 and 73, the tower will host a 1,000-square-metre public viewing deck. This space will be entirely free to access for the general public, effectively breaking the monopoly held by the paid observation deck at The Shard. This upper canopy will also feature dedicated educational classrooms operated in direct partnership with the London Museum, allowing school groups and visiting families to study London’s topography, history, and geographical development from an elevated perspective.

The Podium: The 11th Floor Urban Haven

Further down the structure, at an altitude of 42 metres above street level, sits a massive 2,500-square-metre elevated podium garden. Designed in collaboration with international landscape architects SLA, the garden features a 330-metre perimeter boardwalk offering panoramic views of local historic landmarks, including St Paul’s Cathedral, 30 St Mary Axe (The Gherkin), and the Lloyds building. Notably, parts of this terrace will feature a structural glass floor, looking down onto the bustling city streets below.

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How Does the Project Address Sustainability and Environmental Standards?

In the current regulatory climate, constructing a supertall tower requires meeting rigorous environmental baselines. The design by Eric Parry Architects purports next-generation credentials, focusing heavily on low-carbon construction methods and biophilic integration to mitigate the urban heat island effect.

The landscape design provides an unprecedented five-fold increase in urban greening compared to the concrete plaza of the existing Aviva Tower. According to ecological impact reports submitted alongside the planning documents, the project will achieve a verified improvement in localized Biodiversity Net Gain exceeding 500%. This is achieved through carefully curated forest-inspired planting beds, extensive green roofs, and mature tree groves scattered across the public spaces.

In an analysis detailing the operational efficiency of the tower, author William Eichler of LocalGov observed that the scheme’s approval was heavily influenced by its potential to deliver “high-quality office space” while simultaneously contributing directly to the environmental revitalization of the local area, transforming heavily trafficked thoroughfares from St Mary Axe to Leadenhall Street into highly accessible, step-free green pathways.

What is the History and Timeline of the Project’s Approval?

The journey toward breaking ground on One London has been marked by significant architectural and political delays, spanning multiple macro-economic cycles and a global pandemic that forced a complete rethink of office utility.

First ‘Trellis’ Design Approval

November 2016

The City of London Corporation grants initial planning permission for a tapered, cross-braced tower design nicknamed “The Trellis,” which featured heavy bronze-coloured external diamond bracing.

Post-Pandemic Redesign

August 2023

Prompted by fundamental shifts in hybrid working habits and stricter environmental codes, Eric Parry Architects reveals a completely revised quad-segmented block design, expanding internal workspace capacity.

Committee Deferral

July 2024

The Planning & Transportation Committee defers a final determination on the updated proposal, formally instructing the development team to reassess and address public and civic concerns raised during hearings.

Final Scheme Revision

October 2024

The design team resubmits amended plans, reducing the tower’s street-level footprint, improving accessibility, and incorporating a new external feature staircase with two high-capacity public elevators facing St Helen’s Square.

Official Planning Approval

December 2024

The Planning Applications Sub-Committee officially votes to approve the 74-storey, 309.6-metre configuration, green-lighting the commencement of site preparation works.

Structural Completion Target

2033

Following an estimated 18-month demolition phase of the existing St Helen’s structure by contractor Keltbray, main core construction will commence, heading toward full commercial occupancy by 2033.

What are the Main Controversies and Legal Risks Facing the Developers?

Despite securing political approval, a project of this magnitude carries substantial legal and logistical execution risks. The primary challenge rests on the physical execution of the site clear-out. Demolishing a major 28-storey skyscraper in the middle of a densely packed, historically sensitive financial cluster requires surgical precision.

As recorded in architectural dossiers compiling regional developments, demolition specialists Keltbray are slated to handle the delicate dismantling of the St Helen’s tower, a process expected to take at least 18 months before any foundational work for One London can even begin. Any delays in this preliminary phase risk triggering costly contractual penalties with future corporate tenants.

Furthermore, the developers must navigate complex structural engineering parameters due to the building’s offset core design. To accommodate the wide, open public spaces at the base, the main structural core had to be pushed to the side of the tower, requiring complex load-bearing solutions to guarantee stability under extreme wind shear conditions.

The project also faced significant pushback from heritage conservation groups who argued that the immense scale of the tower would permanently alter the setting of nearby historic assets. However, the City of London’s planning committee ultimately ruled that the clear economic advantages, combined with the substantial volume of free public space, outweighed the aesthetic objections raised by critics. With legal clearances secured and detailed design frameworks finalised, the development coalition is now moving rapidly into the pre-construction phase, setting the stage for Western Europe’s most significant engineering undertaking of the decade.

For an inside look at how London’s skyscrapers are reshaping the urban environment and the strict logistical challenges involved in building them, you can watch Skyline Changes in London which breaks down the complex aviation height limits and multi-billion pound investments driving the city’s latest architectural boom.