Treviso was picked to host a 12-day camp as the conditions are similar to what players can expect when the World Cup begins in Japan in September.

Humidity levels have reached as high as 80-90% in north-east Italy.

"As soon as you step outside everyone starts sweating," said Brown.

"You are absolutely dripping with sweat and that makes ball-handling very tough. It's also hard to keep your core temperature low because you are sweating all the time.

"It just sits on your skin and then heats up even more so you can't get your body temperature down. It's really sunny here as well so you're constantly feeling incredibly hot.

"We have guys coming on and spraying us with cold water and we're constantly trying to wipe the sweat off you so your skin gets the chance to cool down."

Brown was left out of head coach Eddie Jones' initial training squad but the 33-year-old has been given a chance to impress before Jones picks the 31 players he will take to the World Cup on 12 August.

Each player is weighed before and after training and the Harlequins full-back says nutritionists are on hand to make sure they regain the weight lost during sessions by eating properly and hydrating.

"On our first really hard session I lost 3kg of weight. Back in England, I would barely lose any weight from a normal session in normal conditions," said Brown.

"After a Test match, I would probably lose a maximum of 1kg. And that's playing at the highest level under massive fatigue. So that puts into perspective the weight loss that you can get over here.

"Once you have taken all the right things, we will go and eat lunch and you are pretty much back on it by the afternoon session. It's no problem as long as you do the right things."

England return home on Friday to start preparations for the first of four warm-up matches, against Wales at Twickenham on Sunday, 11 August.