I do understand what you are saying and appreciate all the help you are putting in. The problem is that only having a few hard copy BMDs, all you can go on are things told by relatives.
Someone having a southern accent indeed would not constitute coming specifically from London - however, if my father can recall Gordon telling him he "was born behind the Arsenal Football ground", would that not be evidence of him coming from the Highbury area of London? He was also an avid Arsenal FC fan.
My father also states the following based on recollections of 'what his father told him':
Gordon was named after the famous jokey - Gordon Richards.
His mother was French.
His father was a horse breeder.
My father was born in 1947
He has two brothers born in 1948 and 1951 so would this not suggest Gordon's timings for conceiving his sons?
Gordon (according to Margaret's son's hand-me-down stories), had an older family - I am currently trying to obtain more info on this to elaborate whether this meant he had older siblings, or if this is in relation to his 1st marriage to unknown wife no.1 of bigamist marriage.
He served his prison sentence at Armley Jail in Leeds, I am suspecting sometime between 1947 and 1951,
His earlier claim that the BMD office in (?) London (?), burnt down destroying his birth cert, could well be an 'easy way out', of destroying his original name, pinched from Nora's claim of the same.
If the police managed to catch up with him, they obviously had some information that could be the missing link here; original name? Address?
My guess to finding this missing link would either be down to his army service, or within his prison sentence?
If the recorded bigamy sentences already found reveal nothing on a Gordon Richard Markinson, could this be down to him being imprisoned under his REAL name? Could this REAL name be the one held by the Green Howards.
I do intend to do some leg work on this when I get time, as well as scanning in and uploading the documents I hold to somewhere that can be viewed.