Now firmly established in his position as Chair of the City of London Corporation’s Planning & Transportation Committee, Tom Sleigh has brought renewed focus to the capital’s latest developments, while providing fresh perspective on the future direction of the Square Mile.
Last month, Hannah Woodger, Editor of Tall Buildings Magazine, had the opportunity to meet with Tom to discuss the City of London’s ongoing transformation, reflecting on the delicate balance between preserving historic character and meeting modern urban needs, while unpacking the central priorities of the City Plan.
HW: The City’s skyline has changed dramatically in recent years. How does the City Plan 2040 guide where and how that growth continues?
TS: The skyline today is almost unrecognisable compared to 20 years ago – even 10, really. Much of that change comes from the clustering of towers on the eastern side of the City, which I think is fantastic. It shouts commerce, confidence and the image of a global business centre – which, of course, is what we are and what we want to remain.
We already have over 10 planning-approved towers in that area, so in another decade, the transformation will be even more striking. That continued evolution reflects a strong sense of momentum, renewal and business confidence. The City Plan 2040 underpins this direction. Detailed analysis of London’s projected jobs growth and office requirements shows that most of the new workspace will need to be delivered within the Square Mile – particularly in the eastern cluster. That’s largely because much of the Square Mile is constrained by heritage considerations, such as the strategic sightlines to St Paul’s Cathedral.
We have what we call a “jelly mould”, which effectively defines where tall buildings can be built and the height contours within those zones. We know we’ll need at least 1.2 million square metres of new office space by 2040 – probably more – and demand will dictate how much beyond that. With a vacancy rate of just 1.5%, the reality is we can’t build fast enough to keep up. There’s a near-insatiable demand for Grade A office space in the City.
HW: The City is defined by its juxtaposition of old and new. How do you navigate that relationship in planning decisions – and what does a project like 50 Fenchurch Street tell us about that approach?
TS: London has always been a story of renewal. The only constant is change – from Roman times onwards, the City has continually evolved and adapted. That economic imperative is in our DNA; it’s what keeps the City successful. No one values the City’s heritage more than the Corporation. We own a significant portion of it – around 45 to 50 churches, for instance – and we work closely to integrate heritage into every stage of planning.
As you say, it’s the juxtaposition of old and new that defines the City’s unique character. We don’t have a monolithic skyline of glass towers, nor a static landscape of preserved buildings – we have both, side by side. And they complement one another beautifully. Visitors and photographers often capture the two together, because it’s that contrast that’s so captivating. At 50 Fenchurch Street, for example, the medieval All Hallows Staining Tower is preserved on stilts, with 35 feet of space excavated below it. At 85 Gracechurch Street, remnants of the Roman Forum were uncovered and incorporated into the scheme. Similarly, the Roman Mithraeum beneath Bloomberg’s offices has become a free public attraction. Modern developments often amplify and celebrate the City’s heritage rather than diminish it – and that’s exactly the approach we encourage.
HW: How important are tall buildings to the future of the City of London?
TS: Tall buildings are absolutely vital. With 1.2 million square metres of additional office space needed by 2040, and with most of the Square Mile subject to height restrictions, tall buildings are how that growth will be delivered. We’re confident that the eastern cluster is the right location – the City Plan defines it clearly, and Government inspectors have endorsed that approach. Tall buildings will be the backbone of future growth, supported by a strong retrofit agenda for older stock. There’s real optimism in the market right now, and tall buildings will continue to play a central role in sustaining that momentum.
HW: 1 Undershaft will become Western Europe’s tallest office tower. What does a project of that scale need to deliver for the City?
TS: When a developer proposes a major scheme like that, we operate on what I’d call a ‘civic contract’. We provide an enabling, predictable and supportive planning environment – but in return, we expect something back. That “something” is more than just office space. It’s public benefit: sky gardens, cultural or community spaces, improved public realm, or the preservation and celebration of heritage. Developers understand this and increasingly rise to the challenge. 1 Undershaft, which will become the tallest office tower in Western Europe, exemplifies that. Its predecessor, 22 Bishopsgate, is now fully let and commanding the highest rents in the City. It shows that if you build quality space, the market responds. With vacancy at just 1.5%, demand remains incredibly strong.
HW: How do you ensure the City remains a vibrant place to work and visit, not just a collection of office towers?
TS: That’s where our Destination City strategy comes in – it’s our overarching growth plan for the Square Mile. The idea is to create a rich ecosystem that blends business with community, culture and wellbeing. We’re currently mapping ground-floor uses to understand the mix of amenities – and where gaps exist. The next step will be partnering with developers to address those gaps, whether they’re delivering new towers or retrofitting existing buildings. Our vision differs from cities like New York, where many new office towers are self-contained fortresses.
In London, we want permeability – a lively, open city where people can move freely through buildings and spaces. Many new developments now reintroduce historic pedestrian routes, sometimes tracing medieval street patterns. That sense of openness and activation at ground level is fundamental to how we’re shaping the City’s growth.
HW: What are the main barriers to delivering the office space the City needs, and how can the Corporation help overcome them?
TS: The planning system here isn’t the issue – in fact, it’s widely regarded as one of the most enabling and predictable in the world. The real challenges are economic: Construction costs, materials inflation and international financing conditions. These are global issues, not unique to London. But we can help reduce risk through our planning approach. Because we offer such clarity and consistency, developers can plan with confidence. If you engage early and comply with policy, you stand a very strong chance of approval. That predictability helps reduce “planning risk” – which is one of the biggest cost variables in any major project.
HW: What role does retrofit play in the City’s overall development strategy?
TS: The City is leading the way on retrofit. We have a comprehensive policy suite – a Heritage Retrofit Toolkit, a Supplementary Planning Document and clear guidance for developers. The results speak for themselves. Half of all retrofit projects in Greater London are happening right here in the Square Mile, and around half of our new applications are now retrofits rather than demolitions. Encouraging retrofit is important, but making it straightforward through clear policy is what really drives delivery – and that’s exactly what we’ve done.
HW: As Planning Chair, which projects are you most excited to see come forward?
TS: There are several, but 1 Undershaft will certainly be one to watch – demolition of the existing site is already underway. We’ve also just approved 130 Fenchurch Street, opposite 50 Fenchurch – a 31-storey tower that passed planning unanimously in just 38 minutes, which might be a record! It’s an elegant design with a distinctive crown and a public garden wrapping around it. More broadly, we’re seeing a wave of high-quality, innovative architecture coming forward. My aim as Planning Chair is simple – we must never build boring. Every new development should contribute something exceptional to the City’s skyline and streetscape.
HW: To wrap up, what does success look like for a tall building in the Square Mile?
TS: For me, success means excellence on several fronts: High-quality design and materials, strong economic contribution and meaningful public benefit. A successful building supports growth – it creates jobs during construction and provides space for the industries that define London: Finance, professional services, tech. It also offers something back to the public, whether that’s a cultural space, a viewing gallery or improved public realm. And, of course, it adds to the skyline – one that continues to shout commerce, confidence and London’s place as a truly global city.
