The actor said that he only realised that the remake "wasn't a gimmick" after meeting with the film's director Rowan Joffe.
"My first reaction was, 'Are they just wanting to do Brighton Rock meets Heartbeat or something?'" Riley admitted to PA.
Brighton Rock was originally adapted for the big screen in 1947, featuring Richard Attenborough in the role now filled by Riley.
The remake of the film stars the likes of Helen Mirren and John Hurt, and Riley also admitted that it was initially daunting to act opposite such film veterans.
"There might be doubts beforehand and you think, 'Oh my God', but if you start thinking about that when you're actually acting then you're buggered," Riley said of his co-stars.
Riley first rose to fame after playing troubled Joy Division singer Ian Curtis in the critically-acclaimed Control back in 2007.
Brighton Rock was released in cinemas on Friday.