Sorry to pee on your bonfire again, DFC, but I have regularly landed a twin-jet before the threshold at a licensed aerodrome in the UK, with full approval of the airport operator.
Bookworm had a stab at naming some relevant regs, and didn't do badly. However, this is one of those matters which I would consign to my short list of questions for extremely able command course candidates who need to be challenged. There are legislative aspects and practical considerations, there's custom and practice - and history; there's even room for some personal preference.
I would not land a public transport flight prior to the marked threshold, but when flying privately, I'm very happy to do it with accuracy (and the land-owner's permission). It's good for my heart rate, and the brakes!