Cosh Boy (released in the United States as The Slasher) is a 1953 British film noir based on an original play by Bruce Walker.

Led by 16-year-old Roy Walsh, a post-war London street gang specializes in snatching women's purses.

Bob lets them in, and in reply to their enquiry as to his identity, he says he's the boy's stepfather, having just married his mother Elsie that morning.

Then, seeing the belt in Bob's hand, he smiles, suggesting to his colleague they arrest another gang member and come back for Roy later.

The film was based on a play, "Master Crook" by Bruce Walker which had been originally titled "Cosh Boy".

It debuted at the Embassy in 1951 starring James Kenney.The Spectator said "its rough, crude taste is shockingly welcome" and praised the third act for its "highly unpleasant, undeniably effective, melodramatic tension.

[9] Variety said the film was "bound to attract undue controversy" wherever it was screened and felt American audiences would have trouble understanding the accents.

The characters are all stereotypes and in no way arouse the warmth of pity or indignation.... this film may provide plenty of ammunition to those who blame the screen for the incidence of juvenile delinquency.

The awfulness of the crimes committed by the young thugs in the film is in no way emphasised and the excitement of conspiracy and chase is given a glamour which is in no way dimmed by the "nice" atmosphere of the youth club scenes and the puerility of the social workers, who can apparently be so easily duped.

The performance of James Kenney and some good location work are the best points of the film... Joan Collins as the misused young girl is badly miscast.