Plan B was ''surprised'' to be cast in 'The Sweeney'.

The singer-and-actor was shocked when he was offered the role of police detective George Carter, but he was desperate to appear alongside his ''idol'' Ray Winstone in the drama movie and ''couldn't say no'' to the chance to act with the British hardman.

The rapper - whose real name is Ben Drew - told BANG Showbiz: ''I was surprised to be offered this role because there were some great actors up for it as well.

''Ray Winstone is one of my idols and still is so when I was given the opportunity to be in this I just couldn't say no.

''To get to learn from one of your heroes was the best experience and I don't think anything has topped it.''

The 'Ill Manors' star - who was born in East London - was also attracted to the movie remake of the 1970s British TV series of the same name because of its history, and he particularly loved filming scenes in his home city.

Speaking at the UK Premiere of 'The Sweeney' at London's Leicester Square last night (03.09.12), he added: ''It was great to have the opportunity to film in Trafalgar Square, it was extremely exciting. What's great about this film is that it's British.''

The movie's stars Hayley Atwell, Damian Lewis, Steven Mackintosh, Allen Leech and Alan Ford were also in attendance at the premiere as well as Ray and his daughter and fellow film star Jaime Winstone.

'The Sweeney' is released on September 12.