Before my treatment at the Guerlain Spa at Raffles London, top billing went to a remarkable massage at Esperanza in Mexico; intense and at times almost painful but which left me breathing more deeply for days. Schloss Elmau’s incredible offering in the Bavarian Alps came a close second (bonus points for its pools), and I’d have given a bronze to the Mandarin Oriental Tokyo for its Thai-shiatsu treatment.

However, within minutes of lying face-down in the Guerlain Spa – sprawling over four floors of Raffles London at The OWO – I start to mull it over. This treatment is, I think, very likely to sneak into the top five.

Firstly, there’s the bed: it’s everything I want it to be – warm, wide, soft, contoured – but there’s a duvet in the mix too and the parts of the bed where my arms would usually rest – getting uncomfortable after a while on my front – can be dropped down for maximum comfort. Often, after a massage, I could tell you it was lovely but not, with specifics, why but after my exceptionally good therapist Cassie has kneaded and stretched and manipulated my left leg into submission, it feels about two inches longer. She finds spots either side of my spine that I swear have never been massaged before, and delivers perfect pressure, at the perfect pace. I’m now sure: definitely top five.

The treatment also includes LED therapy to complement the effects of the massage; specific wavelengths of light stimulate cellular processes within the skin. When I’m on my front and the LED beams are helping to unknot my back, I can’t feel a thing, although the light of the machine makes the floor shine as if it’s white-hot lava. And when it’s on my face? Well, pretend you’re on a beach without sunglasses, chat to Cassie while she massages your feet and time will fly by. Yes, it’s intense and very bright but it’s also very, very good for your skin and completely non-invasive.

This is all part of the Spirit of London, one of three signature treatments created especially for the Raffles London spa (alongside the Royal Glow Tech facial and Coastal Escape massage) and only available here. And here you must come. It’s 90 minutes of bliss. By the time Cassie finishes working her magic, this treatment is joint top on the best-ever podium and I’m impressed.

L’Atelier Guerlain

I did anticipate good things; greeting me at level B1, the receptionist set the tone. Immaculate in head-to-toe cream with red lips and white-rimmed glasses, she regaled me with a quick history of Guerlain while I enjoyed a rooibos tea. The brand is nearing its 200^th anniversary and its emblematic bee adorns rows of gleaming gold eau de parfum bottles. As befits a grande dame of the fragrance, beauty and skincare industry, Guerlain does things properly and, as such, all possible friction points are removed: slippers are padded; there are small bags inside lockers for wet swimming costumes; the blankets in the relaxation room are weighted; there are two towels per lounger.

Steam room

Vitality pool, alongside the main 20-metre pool

The spa spans a vast 27,000 square feet – almost as much floor space as Regent Park’s iconic white Holme house – and houses nine treatment suites, the L’Atelier Guerlain salon, sauna and steam rooms, gym, studio and a spectacular 20-metre swimming pool. This pool is big, it’s peaceful and it’s gorgeous, accessed via a sizeable, sweeping staircase. The Corinthia around the corner has a nine-metre pool and The Berkeley a 17-metre rooftop offering – sizes typical of many luxury London hotels. In fact, only the newly-opened Emory (22 metres), The Bulgari and London Marriott Hotel County Hall (both 25 metres) trump it. Here, 20 metres feels even bigger thanks to double-height ceilings and beautiful lighting.

Even though there’s a lot to like about this place, certainly one of the best five-star spas in London, for me the treatment was its stand-out star, and the best I’ve had in the UK. Now begins the challenge of finding something to rival it…

Visit raffles.com

Read more: The best spa days in London