Sir Billy Connolly says his life is "slipping away" and he is "near the end" in a new documentary series for the BBC, UK media reports.

Key points: Sir Billy was diagnosed with Parkinson's disease in 2013

Sir Billy was diagnosed with Parkinson's disease in 2013 He says he feels like he is being prepared for the "spirit world" as he ages

He says he feels like he is being prepared for the "spirit world" as he ages He says he sometimes get angry about his condition, but must maintain a "certain calm"

According to British newspaper The Times, 76-year-old Sir Billy discusses his age and battle with Parkinson's disease during an interview in the BBC's two-part series Billy Connolly: Made In Scotland.

Sir Billy was diagnosed with the disorder in 2013, the same year he underwent successful surgery for prostate cancer.

Sir Billy Connolly was diagnosed with Parkinson's disease in 2013. ( Reuters: John Stillwell, Pool )

He is reported as saying he feels like he is being prepared for "the spirit world" as he gets older, as his talents and attributes — such as his banjo-playing prowess — start to deteriorate.

"My life is slipping away and I can feel it, and I should, I'm 75," Sir Billy says in the documentary, which was filmed last year.

"I'm near the end but it doesn't frighten me. It's an adventure, and it's quite interesting to see myself slipping away. Bits slip off and leave me. Talents leave and attributes leave.

"I don't have the balance I used to have; I don't have the energy I used to have; I can't hear the way I used to hear; I can't see as good as I used to. I can't remember the way I used to remember.

"It's like somebody is in charge of you and they're saying, 'Right, I added all these bits when you were a youth, and now it's time to subtract'.

"I can't work my left hand on the banjo. It's as if I'm being prepared for something, some other adventure which is over the hill. I've got all this stuff to lose first, and then I'll be on the shadowy side of the hill, doing the next episode in the spirit world."

Sir Billy says he gets angry his condition will only get worse but he needs "a certain calm" to deal with his battle with Parkinson's disease.

"It's going to get worse. It takes a certain calm to deal with and I sometimes don't have it. I sometimes get angry with it but that doesn't last long," he says.

"The good things are there, the love you have for people is still there and with a bit of luck the love they have for you is still there."

The full documentary, which features personal accounts of Sir Billy's life as well as interviews with fellow comedians, will air in the UK later this week.

Despite his frank assessment of his age and health, Sir Billy strikes an optimistic tone about his future: