Bonsa lever lock
I have never seen that Bonsa LL patern before and I agree:
the style of full stag horn handle slab and a burr replacing the solid top bolster is strange.
The style of lever is common on Bonsa switchblade knives and was still marketed by Robert Klaas company prior the last changes of the weapons' law.
Anyway I have no idea why such knives might be crafted for the British market.
cut