Sir Michael Gambon has decided to stop working in the theatre, bringing down the curtain on an illustrious stage career, after struggling to remember his lines.

Currently starring in Fortitude, Sky Atlantic’s Scandinavian thriller, the 74-year-old said in an interview that it was time to admit defeat.

“It’s a horrible thing to admit but I can’t do it. It breaks my heart. It’s when the script’s in front of me and it takes forever to learn. It’s frightening,” he said.

Gambon, who made his professional stage debut in 1962 in Othello in Dublin, admitted last April to wearing an earpiece on stage through which a prompter could feed him lines. He put his forgetfulness down to age and was worried it was a sign of encroaching Alzheimer’s, although doctors gave him the all-clear and his long-term memory remained sharp.

At the time, the winner of four Baftas and three Laurence Olivier theatre awards said the only roles he felt he could play without prompts were those with very few words but lots of physical possibilities. In an interview with the Sunday Times Magazine, Gambon said he realised six months ago that his days on stage were numbered when he was asked to read for a new play in the West End.

“There was a girl in the wings and I had a plug in my ear so she could read me the lines,” he said. “And after about an hour I thought, this can’t work. You can’t be in theatre, free on stage shouting and screaming and running around, with someone reading you your lines.”

In 2009, he was twice taken by ambulance from rehearsals at the National Theatre to A&E at St Thomas’s hospital in London, suffering panic attacks after he forgot his lines. Gambon, whose memorable roles include a novelist with writer’s block in Dennis Potter’s The Singing Detective, a foul-mouthed crook in the film The Cook, the Thief, His Wife and Her Lover, and Professor Dumbledore in the final six Harry Potter films, has adapted to his diminished powers by taking smaller stage roles with few or no words, including in Samuel Beckett’s Eh Joe in Berlin in May.

His most recent play involved no dialogue at all. “It was brilliant. I just had to do a range of facial expressions,” he said. The one before that, he had to steal glances at lines scribbled on a table, while portraying a blind man.

Gambon said he would continue to work in film and television, where he could be fed lines in small takes or read them off a screen. In the spring he appears in the BBC’s adaptation of The Casual Vacancy, JK Rowling’s first novel for adults, and he plays Private Godfrey in the film version of Dad’s Army, to be released early next year.

Most actors run into the problem of memory loss and devise ways of coping. When the 65-year-old Laurence Olivier forgot his lines during Eugene O’Neill’s Long Day’s Journey Into Night, he concocted a reason for leaving the stage to look them up in the wings. He returned with the audience none the wiser.

Angela Lansbury, 89, resorted to an earpiece for her Tony award-winning performance in Blithe Spirit, which she took to London last year. Richard Dreyfuss, 67, who starred in Jaws, used an earpiece in a 2009 production of Complicit at the Old Vic.

Two years ago, Dame Judi Dench said she took memory supplements because she struggled to remember her lines. Others have carried on stage work well into their 70s and 80s. In 2013, Vanessa Redgrave and James Earl Jones starred in Much Ado About Nothing at the Old Vic at the ages of 76 and 82 respectively.