// I am hoping that the GP was confused as they just can't "do a trial"//
Peter Pedant "if they are gonna do it anyway, then they can - because it is not a trial, they were gonna do it ( Trials being radically different, dice and barred cages and fings oh and monkeys)
Collecting anonymised data after doing something you would do anyway is NOT a trial and is good practice"
Except in this case giving a different vaccine for the second dose than from the first one had been explicitly ruled out in the UK except under certain unusual circumstances.