Possibly
If the store took no reasonable, proportionate action to secure the knife and had foreknowledge of the likely consequences(*), well, yes.
(*)
what is reasonable and proportionate is the question.
If the knife was in a locked cabinet (as it is for the better knives in Lakeland) that is one thing
If the knife was on a table outside the door with a label 'please stab someone', that is another.
Biting the hand that feeds IT
