The Peninsula Spa

The Peninsula London · Belgravia, London

Our assessment: Gold · 85%

The one thing

Two floors underground at Hyde Park Corner there is a 25 metre pool in a chamber tall enough to swallow the sound, tiled a turquoise so vivid it throws colour onto the walls, and above it a ceiling that behaves like a sky, brightening through the morning and dimming to a glow by evening. A mosaic tree canopy runs around the upper walls, so the whole room is quietly pretending to be one of the parks a hundred yards overhead.

The verdict

The Peninsula London opened in September 2023 on the corner where Belgravia meets Hyde Park Corner, looking across at Wellington Arch, and it took the group the better part of two decades to find the site and build it. The building is by Hopkins Architects, newly made on ground cleared of postwar offices, and the spa that sits beneath it is by Peter Marino, who has spent a career doing interiors for houses that do not have to ask the price.

What he was given here was a problem rather than a view. The spa occupies two full lower floors and there is not a window in any of them, so rather than apologise for being underground the design leans the whole way in and builds its own world. The pool hall goes double height, which is the single most expensive decision in the room and the one that makes it. Turquoise tile covers the pool and the whirlpool beside it, the mosaic canopy of leaves wraps the upper walls, and overhead a lighting ceiling tracks the hours so that the room is bright at eleven and low and warm at eight. Music comes through underwater speakers, which sounds like a gimmick and is not, because the moment your ears go under the room changes register entirely.

The parks are the stated reference, Hyde Park and Green Park and the palace gardens, all of them a short walk up the stairs and none of them visible from anywhere in the spa. It is a slightly odd conjuring trick when described and a rather lovely one to be inside. Three semi private cabanas sit at the water's edge with chaises between them, and there is a small mini bar in the changing rooms stocked with juices and things made in the hotel kitchens.

The register throughout is hushed and deliberate. Phones are not allowed anywhere in the spa. Coffee is kept off the poolside menu on purpose, because the smell carries and changes the room, and it comes only if asked for. Guests are handed a tea on arrival, robes are warmed in the treatment rooms, and every locker has a gown, slippers, pool shoes and a jewellery box waiting in it. Small things, but they are the difference between a hotel with a pool and a spa that has thought about the day.

Above the water sit seven treatment rooms, wood panelled and low lit, and a fitness studio open around the clock with Technogym equipment, and Errol Douglas keeps a hair atelier down here too, which is a useful thing to know if the day has an evening attached to it.

The water

The pool is the reason to come and it earns that. Twenty five metres is long enough to actually swim rather than potter, the water is warm without being soupy, and the height of the room means the noise of other people simply rises away from you. Beside it lies a vitality pool, jetted and hotter, for the part of the afternoon when swimming has stopped being the point.

The heat is arranged differently, and this is the one thing worth understanding before booking. Rather than a single mixed circuit, there are two mirrored thermal suites, one for women and one for men, each tucked inside its own changing area and each holding a sauna, a steam room, an ice fountain, experience showers and somewhere to lie down afterwards. Four thermal cabins in total across the two. It works beautifully if you have come alone, and it means a couple or a pair of friends cannot do the heat together, which catches people out.

The sequence, once you know it, is a good one. Heat until it stops feeling like warmth and starts to feel like weight, then the ice fountain, which takes the breath sharply and hands it back cleaner, then a shower, then flat on your back in the quiet until the pull to go again arrives. Then the long pool under its false sky, which after all that reads less like exercise and more like being poured back into shape.

There is nothing outdoors, and there could not be. Anyone who needs sky and cold air will not find it here.

Treatments

Three houses do the work, and two of them came to Britain through this room. Margy's Monte Carlo, the Monegasque skincare line, arrived as a UK exclusive and stays that way, and its facials are the ones with the gold mask, the microcurrent finger and the results people book flights around. Ricari Studios followed from Los Angeles with a lymphatic method that is closer to bodywork than beauty, all long draining strokes and a flatter stomach walking out than walking in. Subtle Energies is the Ayurvedic aromatherapy house and it is the one to choose when the problem is sleep or a mind that will not settle, with Shirodhara doing the thing that oil poured slowly onto a forehead has done for a very long time.

The technology sits alongside rather than instead, with LED, radiofrequency, ultrasound, microcurrent, compression therapy and lasers all on the menu, and none of it injectable and none of it doctor led, so this is a beauty floor with good equipment rather than a clinic.

The nicest part of the menu is the Masters in Residence, a small standing roster of specialists who are genuinely specialists. Doctor Li Ping Bartlett takes the acupuncture and Traditional Chinese Medicine, with something over forty thousand clinical hours behind her, from £250 an hour. Emanuele Calabrese is an osteopath working specifically in pain, and Henry Barratt trains people at £400 an hour, which tells you who is booking him. Two full day programmes fold all this together, one built around sleep at £750 and one around skin at £900, each with a proper lunch and the thermal floor for the day.

Getting in

Non residents are welcome and the spa was always meant to serve Belgravia rather than just the bedrooms upstairs. There are two ways in. A Wellness Half Day Pass is £250 and gives three hours of the pool, the sauna and the steam, and it is also sold through Spabreaks from around £260 a head. Otherwise a treatment earns the water, and the published threshold sits somewhere between ninety minutes and two hours depending which of the hotel's own documents you read, so it is worth confirming the length when you book.

Packages run from a £450 holistic escape up to the Private Couples Suite, which is £900 midweek and £1,100 at weekends and comes with its own jacuzzi and steam room, two ninety minute massages, champagne and two hours of the spa. Treatments are 18 and over. Prices carry VAT and a service charge is added.

Booking goes through the spa on +44 20 8138 6688 or by email, and not everything appears in the online engine, so the phone is the better route for anything unusual. The pool opens early, from seven in the morning, with the spa itself running to nine at night, and the gym never closes. Cancellations inside twenty four hours are charged. Hyde Park Corner station is about five minutes on foot. The spa is below ground and reached by lift, and the showers were built wide for wheelchair users, so do say when you book if that matters and they will make the day work.

What to know before you fall in love

• The heat sits inside two separate single sex suites, so couples and friends can swim together but cannot share a sauna, a steam room or an ice fountain.
• The spa is entirely below ground with no windows anywhere, and the daylight overhead is a very good imitation rather than the real thing.
• The water has to be earned, either through the £250 half day pass capped at three hours, or by booking a treatment long enough to include it.
• Treatments are 18 and over.
• The pool and spa are alcohol free, and there is no outdoor water of any kind.

Best for

Solo swimmers who want a proper 25 metres and a very quiet afternoon. Anyone chasing a facial or a lymphatic treatment they cannot get anywhere else in Britain. Couples, provided they know the heat is separate and the pool is where they will meet again.