I was thinking the same things Maltenby. I've said before on here that there is no such thing as a 'legal trap', only traps that can be 'used legally under specific conditions' and I also suspect that there was never really any investigation into how the trap was set, or whether it had been interfered with or anything else.
The Spring Traps Approval Order states for the MKVI Fenn traps that :
The traps shall be used only for the purpose of killing or taking grey squirrels, mink, rabbits, stoats, weasels, rats, mice and other small ground vermin (except for those species listed in Sche