Fenn traps for use in the UK must be officially tested and on the approved list. Some traps on sale are known to be copies that do not comply with the requirements and their use is illegal within the UK!
Mk 6 Fenn spring trap (right) is UK approved for Rabbit, Mink, Grey Squirrel, Weasel, Rat.
In the UK it is The Law that Fenn traps must always be set inside an appropriate natural or artificial tunnel or a purpose made container.
Always carry out a thorough risk assessment of the proposed trapping area to avoid accidentally catching protected species and non-target domestic animals and pets.