Boris Becker was asked by a prison doctor if he had been self-harming during his time in Wandsworth

In his upcoming autobiography Inside the former Wimbledon champion has described the scrutiny he faced in jail, saying: "Trying to shave with the stubby little razor they had given me, I ended up with nicks on my cheeks and stabby slashes under my chin and down my neck.

"Soon after, I was summoned to a medical with the doctor who asked if I was self-harming. Why would I? My mind was only focused on doing things to protect myself."

Boris adds in his memoir, an extract of which has been published in the Daily Mail, drugs were commonplace within the prison walls.

He said: "As the days went by, I learned that you could get anything you wanted in prison. Alcohol was easy. People made it themselves with sugar, fruit and other things you could buy legitimately with your allowance from the canteen... then there were the drugs.

"Weed, pills, heroin. Sometimes they came in the prison version of internal mail. Up the back passage. Sometimes it was the wardens - someone taking a cut, someone with a weakness or a problem left vulnerable to a bribe."

He also recalled the physical hardship of daily life in Wandsworth.

Boris said: "Some days those showers would be icy cold. You never knew why. It was just another unpleasant fact in a day you don't control.

"Dirt all over the floor, on the tiles. I was lent a pair of flip-flops. Boris, wear them, because we don't know who was there before. The first time in my life I ever showered in flip-flops."

The book recounts in graphic detail the routines and survival strategies he relied upon during his sentence, including finding distraction in teaching classes, reading and regular phone calls with his partner Lilian de Carvalho Monteiro.

Inside by Boris Becker will be published on 25 September by HarperCollins.