He may have been diagnosed with cancer and Parkinson’s disease on the same day – but Billy Connolly says he never feels sorry for himself over his heath issues.

In a candid new documentary to be screened on BBC One tonight, the 81-year-old comedian says: ‘When you get something as big as that [Parkinson’s], you just confront it, make decisions based on it.

‘Don’t think you’ve been badly treated, that you’ve got the bad pick of the straws. It’s not like that. You’re one of millions. Just behave yourself. Relax.’

And speaking of the prospect of dying, he says: ‘It is not the big thing everyone has made it out to be, death. It is nothing. It is just a sudden nothing.’

Recalling how he was diagnosed in 2013, the Big Yin, who now lives in Key West, Florida, with his wife Pamela Stephenson said: ‘It was a funny week.

‘On the Monday, I had hearing aids. On the Tuesday, I got pills for heartburn, which I have to take all the time, and on the Wednesday, I got news that I had prostate cancer and Parkinson’s.

‘They told me on the phone. He said, "Look, we’ve had the results in, it’s cancer." And I said, "Oh, nobody’s ever said that to me before." Pamela was standing behind me and gave me a bit of a cuddle, but I wasn’t unduly worried.’

Connolly had surgery for prostate cancer and received the all-clear a few months later.

In the 45-minute film, Connolly discusses his humble beginnings in Glasgow, the impact of violence in his childhood, his experiences as a shipyard welder, and his transition to comedy – with his appearances on Michael Parkinson’s chat show making him a star.  He also touches on his struggles with alcohol, the influence of his wife, and his friendship with the late Robin Williams.

Connolly says: ‘I’m a comedian, and it’s a nice thing to be, but I’m essentially a Clydeside worker who got lucky.’

Of his childhood, he recalls: ‘It was not a happy time. It was a dark time. It was very violent and I was beaten up by my aunts. It had a profound influence on me. I felt kind of abandoned as a child and trapped.’

He said it was ‘very big’ of one aunt to take on the responsibility for him after he was abandoned by his parents, but adds: ‘Having said that, I wish people wouldn’t do that. I wish they wouldn’t be very big for five minutes and rotten for 20 years. ‘

Connolly is also frank about his previous, damaging relationship with alcohol. He recalls marrying his first wife Iris Pressagh in Glasgow in 1969, explaining: ‘We had a horse and cart to take us to the Scotia Bar, where we got half legless, and then I played a gig that night in Kilmarnock.

He says his problems became worse as he became more famous: ‘I got drunk and threw myself around, and it was a waste of time and energy that happens to a lot of people. 

‘They don’t know how to get rid of the feeling that comes from being successful. It makes you lonely, it picks you as one person with a big light on them, and it’s difficult to live with. So you handle it in different ways. Some people join monasteries. Others get drunk. I got drunk.’

He credits his relationship with Pamela Stephenson, whom he met when making a guest appearance on Not The Nine O’Clock News, for saving him from oblivion, and he has now been sober for 40 years.

However, early in their relationship, and before Connolly cleaned up his act, the couple were subject to intense tabloid scrutiny. 

The comedian recalls one incident when ‘this guy was outside [my house]  taking my picture, and I took the camera and I smashed it in the street.  It was very dramatic, and I had to buy it. I had to pay for it, but it was worth it. 

‘Alcohol doesn’t make you clever, you know. The day I found [that]  out, I was in a phone box in London. I couldn’t get out. I couldn’t work it out. It’s hardly Hampton Court maze, is it? I mean, the phone’s on one of the walls that cuts it down to three.’

And poignantly he recalls having a meal with Robin Williams  just days before he took his life – ‘the saddest day’ – in August 2014.

Connolly says: ‘He phoned me and said, "Let’s have dinner." And during the dinner, he said, "I love you." I said, "Thanks very much. He said, "Do you believe me?" I said, "Of course I do". 

‘I thought, "How weird  for him to say that"…  and he was dead on the weekend. 

‘I always felt that was him saying goodbye. It was a sad day in my life, because I saw his whole career, and it was stunning. He was like a rocket ship. He just took off.’

• In My Own Words: Billy Connolly is on BBC One at 10.40pm tonight