I wonder what the pedalo does as I slip into a waffle robe … I’m at Bellecell, a central London molecular-wellness clinic that offers “hyper-personalised science-based solutions to health” – this place could be a Bond villain’s laboratory on the moon.

I am standing in a hushed, blue-lit underground brick tunnel with Kubrick-white furnishings and so many fascinating toys: EMS suits, laser IVs, and what looks like an exercise bike built into a love boat, with a vacuum for your legs.

As distracting as these things are, I am here to try something specific: a hyperbaric oxygen chamber. I am fascinated by these things. Culturally, they have long been signifiers of megalomania, detachment and anxiety. Michael Jackson had one in his house, which isn’t a great recommendation. The Olympian swimmer Michael Phelps is another fan. But what do these chambers actually do? Do you have to be called Michael to use one?

I climb into a plastic body bag in my hospital booties. Hyperbaric oxygen therapy involves breathing pure oxygen in a pressurised environment. The structure is a semi-circular cage with comfortable bedding, surrounded by thick plastic walls. Once I am inside, a technician inflates the bag. I am basically inside a balloon, which will be maintained at constant pressure, as I breathe 100% oxygen through a mask.

Hyperbaric chambers are mostly used to treat gas gangrene, carbon monoxide poisoning and the bends, while the medical uses of oxygen include wound-healing and reducing the risk of infection. Many people report feeling energised afterwards. I have some oral swelling following dental work, and am interested to see if that goes down.

For some, the close confinement and constant sound of pressurisation will be a recipe for a panic attack. For me, it is heaven. I am what you might call a claustrophile. I have always loved climbing into cupboards and corners, making dens and closing a door on the world. I fantasise about Japanese capsule hotels. Now, I lie and watch a zip close above me. There is a hissing noise. I adjust my oxygen mask and observe star-headed thumb screws being turned to calibrate the pressure. The gauge crawls upwards, my ears are getting stuffy. I swallow as it hits 4psi, equivalent to a depth of nine feet under water. Gazing at ambient blue through a hatch to the outside world, I imagine I’m much deeper, packed into a nuclear missile on the undercarriage of a submarine. I am in my happy place.

The use of oxygen for performance-enhancement is mostly misunderstood. The effects of inhaling it are extremely short-lived. Athletes are often seen huffing cans of oxygen at the touchline, but science indicates that this is a mostly meaningless activity. Pressure makes all the difference. Under pressure, oxygen is dissolved in larger quantities in the blood plasma itself, not just the red blood cells. That means a much higher amount of the gas is transported into tissues that need it for healing, in theory mobilising stem cell release to repair the body quickly. It is definitely promising; the catch is, you would probably need a few treatments to see the benefit. At £160 an hour, post-workout muscle soreness probably isn’t reason enough.

I thoroughly enjoy the experience for its own sake. Lulled by the pressure and soft lighting outside, I fall into a deep, restorative nap. After an hour, I emerge as wobbly as a newborn. I don’t feel supercharged, admittedly. I feel drowsy, and absolutely starving. I’m assured this is normal. I do feel astonishingly relaxed, though. The swelling inside my mouth reduces significantly over the next day, too, for which I can probably thank the chamber.

I would totally have one of these in my house. I miss the missile, but can’t afford to go back. Instead, I’m cursed to walk these normobaric streets, breathing 21% oxygen like everyone else, dreaming of when I had less freedom to move.

Walter White, eat your heart out Could I recreate the effect with hydrogen peroxide, baker’s yeast and a tarp over the bath?

Wellness or hellness? Airs and graces. 5/5