Breathing new life into London’s Old War Office 

In 2023, London’s Old War Office opened to the public for the first time in nearly 120 years.  

Built in 1906, the 1000-room, Grade II listed building served as a workplace for some of the most prominent political names of 20th-century Britain, including Sir Winston Churchill, who famously directed the war effort from behind its walls.  

The Ministry of Defence used the building until 2016, when the Hinduja Group acquired it and embarked on an ambitious renovation project with the luxury hotel chain Raffles.  

Following this seven-year transformation, the Old War Office is now reborn as the UK’s first Raffles hotel and residential complex – marking an exciting new chapter for the building. 

As the lead mechanical, electrical and plumbing (MEP) consultant, we played a pivotal part in the conversion, undertaking the design of all MEP systems – from heating, ventilation and air conditioning to drainage and power. 

We also provided services in sustainability, energy, BREEAM, vertical transportation (VT) and IT/AV to support the building’s redevelopment.  

The OWO: a historic landmark reimagined 

Situated on the site of the former Palace of Whitehall, this was a highly complex project due to its scale, conservation area restrictions and the need to sensitively restore and preserve historic interiors. 

The OWO, as it is now known, contains 120 luxury bedrooms and suites, nine restaurants, three bars, and 85 Raffles-branded private residences. As part of the conversion, a three-storey rooftop extension increased the size of the already colossal structure by 31 per cent. Plus, four new basement levels were added to accommodate a 600-person subterranean ballroom, spa, swimming pool and kitchens.  

We collaborated with EPR Architects and 41 other sub-consultancies to ensure the modern amenities and services were in keeping with the building’s original Baroque features. 

Our approach has been to service the building as a whole – with dedicated systems for each part (both the hotel and high-end residences) where possible. 

Digital coordination, seamless collaboration 

To aid coordination during this major services refit, the whole project team worked in Autodesk Revit 3D building information modelling (BIM) software, which contains more than 1 million design elements – 400,000 of which are related to mechanical and electrical services.  

Before this model was available, we worked with a survey model containing digital scans of the entire building. This was supplemented by digital general arrangement (GA) drawings with embedded photographs, which meant our specialists could click on a GA to reveal a photo of a specific element at any time. 

On-site discoveries were still made, however. For example, when part of the ceiling was removed, a series of WWII-era reinforcement beams were exposed which meant we had to reroute services around them. Therefore, it was the combination of both digital tools and physical inspections that made this project a success. 

Solving complex project challenges  

One of the biggest challenges was routing building services from the basement to the hotel’s upper levels while avoiding listed rooms on the ground floor. To navigate this, our team made use of the ‘moat’ – an existing underground corridor encircling the entire building – to effectively distribute services.  

Additionally, as the largest guest suites that now occupy the former war rooms had listed wood-panelled walls, the panelling had to be carefully removed to accommodate fan coil units. These were installed discreetly behind period-style grilles. 

Due to the building’s listed status, finding suitable locations for equipment was challenging. Every corner of the building was used, as placing large equipment on the roof was not permitted and careful coordination of service distribution was essential. 

Enhancing energy efficiency and environmental sustainability 

Upgrading the sustainability credentials of a Grade II listed building was no easy feat. From the outset, restrictions on materials and the need to maintain listed features also required meticulous planning.  

The building’s high thermal mass plays a key role in its energy efficiency by maintaining consistent heating and cooling, thereby reducing temperature fluctuations. Additionally, a state-of-the-art building management system (BMS) has been installed, enabling operators to accurately monitor energy consumption and make adaptations instantly. 

We also ensured that the building is prepared for future connection to district heating, which will further enhance its energy performance. 

Throughout the seven-year construction period, we adapted to legislative changes and improvements in the hotel operator’s brand standards. For example, we added electric vehicle charging points to the residents’ parking areas to meet the growing demand for car charging infrastructure. 

Proud nominee of the 2024 Retrofit Project of the Year 

We’re proud to have played a key role in this major renovation, which is shortlisted in the Retrofit Project of the Year award at the 2024 Building Awards. 

Thanks to the coordination and collaboration across all teams, this project illustrates how a large heritage building can be rejuvenated – preserving its past whilst breathing new life into its structure. 

While The OWO is now fully open to the public, our work continues with seasonal commissioning post-handover, so that we can fine-tune and adapt the systems as they are being used. 

All images courtesy of EPR architects