There is a common misunderstanding here.My ' birth loco' could be one of several released to traffic in July 1962:
Class 45 D53 Royal Tank Regt.
Class 46 D171-4
Class 40 D396-7
Class 52 D1006 Western Stalwart,
D1035 Western Yeoman
Class 07 D2990-1
Class 08 D4135-9/72-3/86-9
Class 27 D5393-6/8-402
Class 31 D5848-51
Class 37 D6745-7/68
Class 35 D7049-3
Class 83 E3305 (E3100)
Using my exact birthdate would narrow this down somewhat.
The dates quoted for new locomotives, at least from the private sector builders, are not when they were "released to traffic". For example classes 27/31/37 shown here as new in July 1962 means that's when they arrived at Doncaster Works from the manufacturer. The locomotives were only "released to traffic" after successfully completing acceptance trials. This was a much more compressed version of what now is often called "mileage accumulation" where new trains have to run a specified mileage trouble free before being "released to traffic".