followme, if by London you mean TC, there isn't a single watch which hasn't had a validation for 4 years. Do you mean a specific discipline, ie EGLL APC, or TMA? Even then I would be astonished if this were true.
Bear in mind that it's down to a team of OJTI's and watch training and unit management to make the decision to end someone's training and therefore, hopefully, a bigoted opinion would contradict the majority. I've heard some very petty and unfair early judgements being pontificated about trainees but against the reasonable majority they have little weight.
It isn't easy to end someones training. In this day and age of industrial tribunals there has to be a cast iron case and this can mean training continuing for quite a while after it has become clear that the end is nigh. While this is frustrating for the instructor, it does give the student every possible chance to meet the required standard. Ego doesn't come into it.