The actor played the part of the Birmingham gangster across seven series of the BBC crime drama, which came to an end in 2022.
Appearing on Desert Island Discs over the weekend (February 11), Murphy recalled going for the role of Shelby over a decade ago.
“I wasn’t the obvious choice physically,” he admitted. “I hadn’t up to that point played anyone who had that sort of physical presence.
“I don’t know if I convinced [Knight] in the meeting – I don’t know if this is apocryphal or he’s just made it up because it’s a good story, but apparently afterwards I sent him a text saying: ‘Remember Steve, I am an actor.’
“And I do believe that. I do think it is our duty as actors to transform to whatever the part demands, and he was generous enough to give me a go,” he added.
Following the conclusion of Peaky Blinders, there are plans for a film version, with Knight recently revealing that the script was almost done.
“I’m just working on the final bits of it at the moment,” he told the Radio Times. “I just sit down at the keyboard and start. It’s a bit like having a dream, for me. You sit there and all this stuff comes, and then you read it back and think, ‘That’s pretty good – but where did it come from?’
“The plan is to start shooting that in the middle of ,” he added.
The film is expected to be set during and after World War II, with Knight previously suggesting it will be “the same but different” to the show.
Murphy has recently been earning praise for his starring role in Christopher Nolan’s Oppenheimer, landing his first Oscar nomination for playing J. Robert Oppenheimer in the film.
Recalling where he was when he learnt of his Academy Award nod, Murphy explained to Deadline that he was “sitting around having tea” at his parents’ house before “the phone started popping”.
The actor has also opened up about the lengths of detail he went to portray the father of the atomic bomb in the film.