Sofitel So SPA

Spread over three floors of the Sofitel St James hotel, So Spa is a little haven of French pampering set in the former banking hall of Cox's and King's. You're in the heart of tourist London, just a few steps away from Trafalgar Square and St James Park.

A friendly porter, complete with bowler hat, directed us to the spa's reception. The spa décor is French chic: dressed in sumptuous deep pinks and purples, furnished with silk drapes, candles, velvet upholstery and dark woods. A pretty rose trellis decoration, Rennie Mackintosh-style, runs throughout the space.

Upon arrival, Marina greeted me with a friendly "bonjour". She offered a welcome tray of hibiscus tea laced with honey, a chocolate-covered apricot, and a welcome hot towel to wipe away the grime of the Central Line.

The spa is small but perfectly formed: the reception, several manicure stations and tea bar are on the ground floor; a staircase leads up to a mezzanine with five treatment rooms and a relaxation suite; and a lift descends to the lower basement where you'll find the changing rooms, hammam and Jacuzzi. Although some of the spa is below ground level, natural light filters through so the spa never feels claustrophobic.

The changing rooms are immaculate with plenty of spacious lockers, piles of fluffy white towels, a vanity table (well-stocked with deodorants, hair styling products and body lotion), three showers with shampoo and conditioner, and a communal changing area which is perhaps a little on the snug side.

Like many central London venues, So Spa sadly lacks a swimming pool. Instead, try the private hammam decorated with mother-of-pearl mosaic tiles which would comfortably seat four, or the more intimate bubbly Jacuzzi if you're visiting by yourself or as a couple. The spa recommends chilling out in the Jacuzzi and steam room before your treatments. This is normally free with treatments lasting an hour or more; if not, there's a £10 fee.

Depending on which treatment you're having, you could also try the hydro-pool in the double treatment room, or the chromotherapy bath in one of the individual treatment rooms.

Relax post-treatment in the quiet relaxation room on the mezzanine level. Here, there are three wooden loungers with squidgy white mattresses, each with their own noise-reduction headphones playing a range of relaxing tunes, and glossy magazines. Help yourself to citrus- and cucumber-infused waters or teas from assam to white peony.

We had the Cinq Mondes Ko Bi Do Facial Ritual (60 minutes, £100).

Romane, my therapist, began the treatment by spritzing my choice of perfume into the room -- I chose Egyptian Water, based on lotus, cumin and rose -- and adjusting the bed so I was comfortable. She checked whether the music, the temperature of the room, the temperature of the bed and the lighting were to my taste; the room was completely personalised.

Romane applied a spritz of floral toner to my face, gently rubbed in a soft cleansing balm, then followed with a beaded scrub. Post-exfoliation, my skin was a little on the sensitive side. Romane picked up on this immediately, prescribing and applying a soothing oil-based treatment serum. She inspected my skin and pronounced that it was dehydrated, recommending a serum for future use.

Romane used two masks for the treatment. The first was based on kaolin and herbs: its slightly medicinal smell grew on me. Romane warned that the mask might tingle but, in fact, it felt very calming. While the mask set, I enjoyed a deep arm and hand massage. The second was a hydrating sheet mask which felt cool on the skin and had a nice, if temporary, plumping effect.

Romane removed the sheet mask and started a facial massage, using a gentle pulling and rolling technique and tapping movements on my face and décolletage. Romane said the massage gently encourages the microcirculation. She cleansed my skin once more and applied a finishing moisturiser. My skin felt smoother, fresher and glowing afterwards.

So Spa draws on its French heritage offering Cinq Mondes and Carita face and body treatments, traditional hammam treatments, and treatments designed for men and mums-to-be. If you're looking for something new, try the Marisa Berenson treatments. The cult, all-natural American range -- exclusive to So Spa -- is based on unusual essential oils and prickly-pear oil.

You can also combine a quick treatment with a little alcoholic indulgence: a martini (made your way, bien sur) and manicure.

You can eat lunch or afternoon tea at the tea bar, a communal table on the ground floor of So Spa. We indulged in a delightful afternoon tea of mini sandwiches, three different scones and mini patisserie, including one of the loveliest macarons we have ever tasted. Service was impeccable throughout.

If you're looking for something savoury, you can also order from the menu at the hotel's Balcon restaurant which includes steak, burgers, fish and lighter salads.

We loved

The ability to customise treatments and your treatment room to your taste.

Despite its grand location, So Spa has a lovely, friendly feel to it -- and the customer service is excellent.

The delicious afternoon tea, in true grand London hotel style, was a real highlight.

We didn't love

Although it was undeniably popular with guests, the bubbles in the Jacuzzi felt a little lacklustre to us.

When we visited, building work was taking part next door. No amount of relaxing spa music can drown out the sound of a pneumatic drill.

Couples, mothers and daughters, or best friends: So Spa is a perfectly intimate space to catch up.

Francophiles looking for a little piece of Paris in London.

We awarded Sofitel So Spa a Good Spa Guide rating of 5 bubbles. The spa is beautifully finished, the service is flawless, and the food is exquisite. We would return tout de suite.

Super Spy visited in October 2016 and awarded it 5 Bubbles.