Share this post

Standing since 1906 in London's historic Whitehall district among government edifices, the Old War Office building has a storied history, having served as the administrative centre for the nation's military leadership, including Winston Churchill, and even inspiring Ian Fleming's James Bond novels. With its impressive Edwardian Baroque exterior and beautifully restored interiors, the Old War Office was until recently the location for Defence Ministers and members of the Defence Council.

After eight years of restoration, this iconic building has been reborn as The OWO, a new destination that includes a luxurious hotel with 120 guest rooms, Raffles London at The OWO, 85 branded residences, The OWO Residences by Raffles, , a capacious 600-person ballroom, a spa, nine restaurants, and three bars. The Old War Office building, designed by architect William Young in 1898 and completed by his son Clyde Young, comprises 26,000 tons of Portland stone, boasting a trapezoidal structure housing 1,100 offices connected by 2.5 miles of hallways, accommodating up to 2,500 people at times. The new hotel allows guests to stroll to No. 10 Downing Street and the Churchill War Rooms, making it a unique window into history, whilst residents have access via a discreet entrance on Whitehall Court, still known as the Spies Entrance.

Jensen Hughes’s team of engineers has been actively involved since 2016 and was responsible for developing a comprehensive fire strategy that reflects The OWO’s esteemed status and demonstrates a sensitivity to its historic architectural heritage.

As a prominent mixed-use building, our journey required solving complex fire engineering challenges. The key challenge was seamlessly integrating connections between the residential and hotel areas and developing innovative strategies for escape and firefighting. In addition, we meticulously designed robust escape and firefighting strategies that integrated into the building's extensive cores and corridors. These efforts were crucial in ensuring the safety and preservation of this iconic structure.

To support extended travel distances in hotel corridors, we implemented the use of smoke extract, which was validated through computational modelling. We used advanced software and simulations to predict how smoke and heat would behave during a fire and how the smoke extraction system would perform in real-world scenarios. Within the residences, we supported extended travel distances by utilising the large-volume hallways and providing automatic fire suppression, a strategy validated through computational modelling.

Furthermore, we employed intelligent signage to maximise the flexibility of ancillary spaces connecting to escape routes, guiding occupants based on the fire scenario. We made informed decisions to omit fire suppression in rooms of particular historical value to preserve the existing fabric without compromising safety.

The renovations enabled the preservation of the building’s historic elements, including its magnificent marble staircase, intricate mosaic floors, and rich oak panelling, effectively striking a harmonious balance between opulence and heritage preservation.

Project Details

Project Owner

Westminster Development Services


Westminster Development Services

Project Location

7 Horse Guards Ave, London

Project Size

760,000 sq feet.



Estimated Project Cost

£1.2 Billion

Featured Experts

Nick Harvey

Managing Director, England, Fire Engineering

BEng (Hons), Fire Engineering, Chartered Engineer, Member

View Details

More from Jensen Hughes