Guerlain Spa at Raffles London, The OWO

Raffles London at The OWO · Whitehall, London

Our assessment: Gold · 86%

The one thing

Guerlain has one spa in the United Kingdom and it sits under the old War Office on Whitehall, three floors below the pavement. Twenty seven thousand square feet of it, arranged around a twenty metre pool set beneath a double height ceiling, inside a building most of London has only ever walked past.

The verdict

The Old War Office is one of those buildings you register without ever expecting to go inside. William Young designed it and his son Clyde finished it, Portland stone and Edwardian Baroque, bowed corners with cupolas on top, and a marble staircase rising under a glazed dome that is still the first thing anybody photographs. It was the War Office through two world wars and served the Ministry of Defence long after, and then it emptied, and it took a very long restoration by EPR Architects to bring it back as The OWO, with Raffles in the hotel floors and eighty five apartments above.

The spa went the other way entirely. Rather than take one grand room and fill it with treatment beds, Goddard Littlefair took four floors, three of them underground, and made something deliberately unlike the building over its head. Where the staircase is theatrical the spa is hushed, and where the lobby is marble and gilt the spa is soft, low lit and close. You come down in a lift and the city stops, which in central London is worth more than any view.

That descent is really the whole experience, and it is why the absence of daylight down there reads as luxury rather than as a compromise. Nothing arrives from outside. No traffic, no weather, no sense of the hour, just warm air and quiet and the long line of the pool under its high ceiling. People swim there properly, lengths rather than lolling, because it is twenty metres and usually close to empty, and then they lie down beside it and stop.

Guerlain is the reason the spa takes this form, and the house treats it seriously. This is a perfumer of nearly two hundred years standing with only a handful of spas anywhere in the world, and the London one carries treatments made for it alone. The Royal Glow Tech Facial was developed for Raffles London and puts microdermabrasion together with photo biomodulation light, and Spirit of London is a massage written for this address and offered nowhere else, aimed squarely at people who have come off an aeroplane wound tight. Andrea Hurst brings her reflexology here, which is an unusual thing for any hotel spa to be able to say.

Alongside all of that, and slightly at odds with it, sits Pillar Wellbeing, which runs the gym, the movement studio and the juice bar. Pillar is a performance operation rather than a spa one, with coaches, recovery work, nutrition and physiotherapy, and it gives the place a second personality Guerlain does not have. The two halves sit side by side rather than blending, and depending on why you came that is either a bonus or simply somebody else's floor.

The water

The pool is the point. Twenty metres, warm, and set beneath a double height ceiling so the room carries the volume of something above ground even though it is nothing of the kind, with the light low and even across it. It is the rarest thing in a central London hotel, a pool long enough and quiet enough to genuinely swim in, and it takes the place a country house spa would give to a view.

Everything else is smaller and gathered into one warm sequence beside it. The thermal suite holds a vitality pool with its jets, a sauna, a steam room and experience showers, which is enough to move between and not enough to call a circuit. Nobody should come here for the heat. There is no hammam, no salt room, no ice and nothing outdoors, so the sequence works as a way to loosen before a treatment or warm through after a swim rather than as a journey with its own shape. Set against twenty seven thousand square feet, it is the one place where the scale of the spa does not show.

A relaxation lounge sits off the treatment floor, and there are day beds and loungers around the pool as well, which is where most people end up.

Treatments

Nine treatment suites, every one of them with its own shower and changing room, so a visit can happen almost entirely behind a closed door. Three are VIP suites, one single and two double, and those add a soaking tub, which turns a treatment into an afternoon. The Royal Spa Suite and the Cupola Spa Suite are the pair the packages are built around, and the three hour Royal Spa Suite Journey folds in a bath ritual, two hours of tailored work, and a fruit platter and a glass of champagne for two, which tells you the register being aimed at.

Guerlain is the only house on the menu and its ranges do most of the work, with Abeille Royale and Orchidée Impériale running through the facials. Beyond the treatments made for London there is a straightforward and very good spine of massage and body work, scrubs, wraps and a personalised massage under the intensive body therapy heading, all of it delivered by therapists Guerlain trains itself. L'Atelier Guerlain sits up on the ground floor with tall windows onto Whitehall, doing hair by SALON64, shorter express treatments and the shopping, which is a sensible separation, the long work below and the light touch above.

Pillar's side runs one to one coaching, mobility and assisted stretching, breathwork, compression, nutrition and physiotherapy, and members get classes and a wellbeing review with it. It is not a clinic and does not pretend to be, but it is a real offer rather than a gym with a towel service.

Getting in

Anyone can book here, which is not true of every spa of this rank in London. Treatments and the published journeys go through the spa directly, on +44 (0)20 3907 7370 or by email, and the pool, vitality pool, sauna, steam room and experience showers come with the booking. What does not exist is a facilities only day pass, so there is no way to simply buy a swim.

Treatments run daily from ten in the morning until seven at night, and the pool and gym open earlier, half past six on weekdays and eight at weekends. The spa opens every day of the year, which matters more than it sounds if you are trying to find somewhere on Christmas Eve.

Prices are kept off the website. Packages sold through booking partners start around £315 a head, and the Royal Spa Suite Journey sits near £670, but the current menu takes a call. Family swim time runs daily, morning and late afternoon, and belongs to residents and hotel guests rather than day visitors. A lift goes all the way down to the spa, and there is an accessible changing room and a pool hoist.

What to know before you fall in love

• The thermal offer is compact for a spa of this scale, one sauna and one steam room with experience showers and a vitality pool, so the heat is a companion to the pool rather than a journey of its own.
• There is no facilities only day pass, so a visit means booking a treatment or one of the published journeys.
• Three of the four floors sit below ground and the spa has no daylight and no view, which is part of the seclusion and will not suit everyone.
• The spa keeps its price list off its own website, so the current menu takes a call or an email.
• Pillar Kitchen sits on the ground floor rather than inside the spa, so lunch means changing and coming back up.

Best for

Couples, and anyone arriving in London who wants somewhere to disappear for an afternoon. A gift that will land properly. Swimmers, which is a rare thing to be able to say about a city hotel spa.