The British stage and screen star snubbed the offer of a role in 1967 film Camelot alongside Vanessa Redgrave as it called for him to show off his vocal skills and Stamp was convinced he would make a fool of himself.
He has rued his reluctance ever since, so when the chance came to prove himself 45 years later in Unfinished Song, he leaped at the chance - especially as, by bizarre coincidence, Redgrave also has a role in the musical comedy, which is titled Song For Marion in the U.K.
Stamp tells U.K. TV show This Morning, "It made me nervous before I agreed to do the movie. But the fact is that I had turned down Camelot years ago and it was something that I had always, always regretted.
"I turned it down because I was frightened because I couldn't sing. And when this job came up I was equally frightened, but when I heard that they got Vanessa to play the wife I thought, 'Wow! She played Guenevere (in Camelot), my character (in Unfinished Song) is called Arthur, and I have got to sing', and I thought maybe the universe is giving me a second bite at it."