I don't often write negative reviews but I have just watched this film and was surprised at its high rating.
On the positive side, Gordon Jackson pulled out a convincing portrayal of an erstwhile ex-con who had been in prison because of one foolish decision. A couple of other actors gave solid performances, some just read their lines and picked up the pay packet.
In the film, Sam Kydd plays a blackmailer and former inmate of Jackson, quite a hefty part for him, sadly here we get a clue as to why he rarely got a major role. He makes a good effort at the character but cannot decide on what personality he has veering between just some bloke needing the cash to occasionally something darker. At no point does he give one a sense of threat.
The film seems heavily edited (yet still drags) with characters appearing in places rather than entering them. One character (a friend of GJ) appears as a witness at the police station sitting confidently astride a chair "a la Christine Keeler" (thankfully clothed) assertively telling detective what he knows.
I found the denouement unbelievable with nothing backing it up, an ending that felt tagged on, a script that meandered and somehow reached its mooring, the port of call unsurprising for a film of this period.