Meanwhile, I've found more info on our hero in a book of memoirs by the solicitor (?) Joe Beltrami, who was responsible for his defence on several occasions. Below is but a short extract from the foreword. Beltrami tells Johnny's story in much greater detail (and very affectionately) later on - too long to post, I think, but it should in due course appear in My Songbook.

[1988:] Johnny Ramensky [...] had a lifelong compulsion to break into whatever he was outside [of] and out of whatever he was inside [of]. Johnny was a true amateur, almost a caricature, a sort of Laurel-and-Hardy criminal. Not only did he blow an empty safe on that occasion [in Rutherglen] - and use such an excess of TNT that two somnambulant constables strolling half a mile from the bank were knocked on their backs by the explosion - but he overlooked a locked drawer which contained more than £80,000! He just couldn't ever get it right. He was a real Charlie Chaplin character, with the same endearing charm. [After his final acquittal, he] returned to prison, where he died - and where, for most of his life, he had also lived. (Sir Nicholas Fairbairn, foreword to Joseph Beltrami, The Defender. Beltrami's tales of the suspected 4 f.)