Close-up: Clarke Peters

Where does the actor go after Lester in 'The Wire'? Nelson Mandela, of course

"I'm an overnight sensation after 36 years," says Clarke Peters, an American who has lived and worked in London for several decades. The 57-year-old is a West End veteran – most notably, he created the Olivier Award-winning musical Five Guys Named Moe and starred in Trevor Nunn's Porgy and Bess. But nothing prepared him for playing Detective Lester Freamon in The Wire, the Baltimore-set drama series, which continues to attract fans long after it wrapped. "I'll walk down the street and people go, 'I watched you last night!' I'm like, damn, I did that three years ago."

Peters' latest role is set to be one of his most memorable. In Channel 4's one-off drama Endgame, the actor plays Nelson Mandela during the last days of apartheid. Was he wary about playing the most iconic political prisoner in history? "Absolutely," he says. "I was wary of not playing how I feel about him, but I tried to put myself in his position, being isolated from the world for 27 years." The actor was obviously moved by his brush with Madiba, as he fondly calls Mandela. "Acting sometimes gives you an insight that's deeper than just reading a biography. I had the opportunity to talk with inmates who were in prison with him, who worked with him. It was more than just a gig, it was a blessing."

Next up, Peters is teaming up once again with David Simon, the creator of The Wire, for Treme, a series set in post-Katrina New Orleans: "Another critical analysis of society," he muses. Plus, he's "sort of hankering to get back on stage", although he's loath to admit whether he prefers the theatre to TV. "My favourite is working and getting paid at the end of the week," he laughs. "That's my favourite!"

'Endgame' is on Channel 4 on 4 May at 9pm