The emerging silhouette of 10 King William Street, a new landmark office for the City of London from Places for London and Helical plc, is now plainly visible after the team marked the on-schedule completion of the building’s structure on 12 January.

Joint venture partners Places for London, Transport for London's property company, and Helical plc were joined by funders HSBC and by McLaren Construction to tighten the final bolt on the steel frame during a traditional topping out ceremony.

Guests took in the vistas of St Paul's Cathedral that future occupiers will enjoy from outdoor terraces on the top three floors.

The eight-storey scheme, with basement and mezzanine, wraps around and above the new Cannon Street entrance to Bank station, one of the Underground's busiest hubs. It will provide 139,000 sq ft of office accommodation, 7,260 sq ft of external terraces, 1,950 sq ft of ancillary retail and a broad range of occupier amenities, including a comprehensive wellness suite. The project targets BREEAM Outstanding, NABERS 5* and WELL Platinum certifications.

The new Bank station entrance, which opened in February 2023, both eased passenger flows for thousands of users and unlocked land that enabled the development to proceed.

The steelwork features beams up to 20 metres in length radiating from a concrete core, creating largely open, column-free floorplates of up to 22,423 sq ft.

Construction began in June 2024 and is due to complete by December this year. The new facade will comprise precast panels with factory-installed windows and aluminium cladding. The stone and brick facade of the former building on Abchurch Lane was carefully removed brick by brick for restoration and will be reinstated on the new structure.

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Building directly above a live Underground station has been a key challenge. Although the station’s concrete box was designed to carry the loads of an over-station development, the team is following detailed methods to minimise vibration and avoid any disruption to services. A 1.8-metre-thick raft foundation supports the steel structure and removes the need for piling around the tunnels.

The programme includes multiple pathways to train and upskill Londoners. Apprenticeships are being delivered through local colleges and universities, alongside internships, work experience and opportunities for T-Level students. Vacancies and placements have been promoted through the job brokerages of the City of London and neighbouring boroughs.

Matthew Bonning-Snook, Chief Executive of Helical, said: "Our topping out ceremony marked a key milestone in the delivery of 10 King William Street, a highly sustainable and amenitised office building in the heart of the City that is attracting interest from a number of potential occupiers. This is the first project in our joint venture with Places for London and we are excited to bring forward this best in class asset before the end of this year."

Graeme Craig, Director and Chief Executive at Places for London, said: "This is a fantastic milestone to reach at our first development through the Platinum Portfolio joint venture between Places for London and Helical. Here, at 10 King William Street, and working together with McLaren, we are bringing about new, valuable and sustainable office space in the heart of the City of London –building and realising a vision for the future.

"This topping out ceremony celebrates the incredible partnership we've built with Helical and partners across the industry to deliver not just 10 King William Street, but also our wider Platinum portfolio, with exciting progress expected this year at our sites at Southwark, Paddington and Farringdon, and even more to follow."

Darren Gill, managing director for London & South at McLaren Construction, said: "Despite the familiar technical challenges of working above one of London’s busiest and most complicated Underground stations, this impressive building is taking shape on schedule. In the process we’ve been able to improve on an already sustainable design by reusing some existing materials and substituting some high quality, low carbon alternatives.

"Keeping to programme is down to some rigorous management systems and toa confident and expert team of up to 240 people on site daily. Those experienced people are providing a great grounding to those colleagues across the supply chain, including 12 apprentices, who are working in construction for the first time and will be using this prestigious project as a springboard for long careers."

The joint venture's project team includes Fletcher Priest Architects and structural engineers Robert Bird Group. Alongside main contractor McLaren, contributors include Keltbray (concrete core, basement and ground floor slab), Bourne (steel frame), Dornan (MEP), Techrete (precast facade), GIG (curtain wall), PAYE (retained facade) and Kone (lifts).