The head robbers home in Hampstead is called 'Dunrobin' ('Done robbing').
This film is made by Butchers. Butchers has triple meanings in English, in that it can be a charcuterie, or an absolute cock up (charcuterie again), or to look at something (butchers hook) It is unclear, from the evidencial information provided in this most excellent film, which Butcher is most paramount.
This film is curiously prescient of the later 'Minder' series. Anthony Booth's character Terry McKinley is but a syllable away from Dennis Waterman's Terry McCann. 'Minder' regular Glynn Edwards has a prominent role. The visit to Wormwood Scrubs is a common motif in 'Minder', and Derek Francis' suavely resigned surrender at the conclusion, while puffing on a cigar, is a dry run for Arthur Daley. A further coincidence: Francis' character is named 'Jack Carter' - a name which is a portmanteau of the first and last names of the lead characters in another Dennis Waterman show - The Sweeney.
One of two consecutive crime b-movies by a British production company called Butchers, written & directed by Jim O'Connolly, and with several of the same actors (playing side-characters) on board... followed by Smokescreen in 1964.
The second crime b-movie starring Jacqueline Ellis where Jim O'Connolly is involved: He wrote and directed this, and wrote The Traitors two years earlier.