Actors Denzel Washington and Russell Crowe have spoken about having the original ‘American Gangster’ watching on set as they made a film about his life.

The story of Harlem mob boss and drug lord Frank Lucas, which will be told in cinemas across the UK this Friday, was overseen by the man himself as he observed from a wheelchair on the sidelines.

Washington expressed his respect for Lucas – now in his 70s – but acknowledged he was responsible for killing countless people.

‘Had he gotten a formal education, had he gone in a different direction, had he had different influences, I think he still would have been a leader or a very successful man,’ he said.

Crowe, who plays a police officer in the film, said of having Lucas on set: ‘It’s incredible when you’ve actually for the source, still alive, still erudite, still willing to discuss things with you.’

After the collapse of his empire, Lucas became an informant and helped convict more then 100 people on drug charges.

As a result his 70 year sentence imposed in 1976 was reduced.

In an earlier interview with New York magazine, Lucas said he was impressed with Washington’s performance.

‘He did a hell of a job. Nobody in the world’s as good as Denzel.’