First of all, and before Sherlock Houses takes me to task, accept my apologies for saying in my earlier post that the Bedford milkman was 'Draycott' as per my even earlier posts the correct name is Drayton.
Apropos witnesses in Bedford and Essex, whilst browsing today I saw this this report
from a few years back. It amused me anyway.
As to the law, I think it would for the Court of Appeal to quash the conviction if there had been a fundamental flaw in the trial process, even if other evidence established guilt beyond reasonable doubt. If a retrial were possible, then in those circumstances, one would be ordered. Because of the execution of Hanratty and the passage of time, a retrial could not really have been ordered.