In the second pub scene, the elderly gentleman in the middle of the trio at the bar is director, Alex Gylanders, father, Mick.
The guy who receives drugs off Tommy at the end of his road is Will Aylward, who did some of the music for the film. He is also director, Alex Gylanders, best friend.
The Profession was originally done as a short film by Alex Gylanders, whilst at college, and was highly praised by his class mates and lecturer, Tony Richardson, which made him write the script into a feature film.
Although some extras were casted, often crew members were used. Including casting director, Holly Ward, who is behind the bar in the pub, and Alex Wallace, and Henry Buss, who play the friends of James, also in the pub.
The drugs seen in the film were a concoction of casting sugar, parsley, and aspirin.