The measurements are done. The scientists know how my body performs in a pleasant 21C. So the fans kick in and a cool breeze gradually lowers the temperature in the chamber.

“Your brain is tasting your blood as we speak and it’s tasting the temperature and the brain is now sending signals to the rest of your body,” Prof Bailey tells me.

The goal is to keep my core – that’s my major organs including my heart and liver – at around 37C.

I was still unaware of the profound changes happening inside my body, but there were already clues on the outside.

By the time the room has dropped to 18C I was no longer sweating and the hairs on my arms were starting to stand up to help insulate my body.

“Science tells us that 18 degrees is the tipping point… the body is now working to defend that core temperature,” Prof Bailey shouts over the droning fans.

Next my fingers turn white and they feel cold. The blood vessels in my hands are being closed off – known as vasoconstriction – in order to keep my warm blood for my critical organs.

This would happen even more quickly if I were a different sex.

“Women do tend to feel the cold more, because of hormones (oestrogen) their blood vessels in their hands and feet are more likely to constrict… and that makes us feel cold,” says Dr Clare Eglin from the University of Portsmouth.

My first shiver kicks in at 11.5C as my muscles begin to shake to generate heat.

At 10C the fans shut down. I’m feeling uncomfortable, but not freezing as we repeated all the bodily measurements again at the lower temperature and it soon became clear I was wrong to doubt that 10C would affect me.

“The body is working jolly hard at 10 degrees,” says Prof Bailey.