Actor and comedian Rob Brydon has said it was difficult to stay in character while playing the role of a legendary actor portraying a man who was frequently too hungover to do his job.

He was speaking to BBC Radio 4's Today programme about his role in new radio drama, Peter O'Toole Is Unwell.

It encompasses O'Toole's critically acclaimed stage role in Jeffrey Bernard is Unwell in the West End in 1999, along with his universally panned performance of Macbeth in 1980.

Brydon, who grew up in Baglan, Port Talbot, said taking on the role "felt like a challenge once we got into the studio" and he battled "to stay on the saddle" to remain in character.

The 61-year-old, known for his role as Uncle Bryn in Gavin and Stacey, said he initially thought "I could probably get close to his voice but there were a lot of words" written by award-winning playwright Terry Johnson.

The title of the audio drama is a riff on Keith Waterhouse's play Jeffrey Bernard Is Unwell, in which O'Toole played the title role of journalist Jeffrey Bernard to rave reviews in 1999.

In Jeffrey Bernard Is Unwell, Bernard is accidentally locked in his favourite London pub overnight after falling asleep in the men's toilets.

He helps himself to a bottle of vodka and reflects on his colourful life.

Peter O'Toole Is Unwell is set in the actors dressing room in the Old Vic in London, where the actor performed in both Jeffrey Bernard Is Unwell and Macbeth.

It is said to explore themes such as success, failure, love, ageing and the pain of coming to terms with who you really are.

Brydon said the play was a "wonderful script" based on the words of O'Toole from sources such as publications and memoirs, praising the "rhythm of his speech".

He said it was challenging "trying to get the essence of somebody else", adding that "it's as if you sort of drift... it was a constant battle to kind of stay in the saddle".

O'Toole was nominated for best actor in the Academy Awards on eight occasions, including for his portrayal of Wales-born army officer and writer TE Lawrence in 1962 film Lawrence of Arabia.

He was given an Academy Honorary Award for his entire body of work in 2003 and died aged 81 in December 2013.

Rob Brydon stars as Peter O'Toole in award-winning playwright Terry Johnson's debut drama for BBC Radio 4.

Describing O'Toole as having "one of the most beautiful voices to listen to", Brydon said he found himself still speaking in his voice after recording it "and I would find myself thinking 'oh, I wonder how Peter would say that'".

Brydon said O'Toole's Macbeth did well on ticket sales "but only because people wanted to see it because they heard it was terrible".

"And then years later he's back in that same dressing room, and he was the talk of the town, the toast of the town, for Jeffrey Bernard [Is Unwell]," he added.

"It's a lovely dramatic device. So when he's there, doing Jeffrey Bernard, he's looking back at what he experienced with the Scottish play all those years ago."

Brydon has also finished filming a new episode of The Trip with fellow actor and comedian Steve Coogan, where they play exaggerated versions of themselves.

The Trip is directed by Michael Winterbottom and follows the pair as they travel around the world and dine at different restaurants, visiting Scandinavia this time in The Trip to the Northern Lights.

"It's delightful, we get to have our cake and eat it really, because Steve Coogan and I play versions of ourselves and it's very bickering and very passive aggressive, or some of it is, other times just aggressive," he said.

Brydon said this was not the reality of their relationship, "but you just look for seeds of truth and exaggerate them for conflict and comic effect".