That's why I asked - if it's from a DVLA database search then I'm a) quite impressed, b) a bit disappointed that it's not done here, where three or four have gone within the last few months, and c) surprised that the envelope was hand written.
But since the envelope was handwritten, it could have been from a watchful PC noticing a Landy on a drive and writing the envelope there and then, having got the owner's name from DVLA.
Similarly it could have been an observant reprobate as above, wanting to convince the owner to buy a device that can be bypassed as Wimblowdriver suggested, having found the owners name with a quick web search.
But my favourite is that it's the owner of the Thatcham site, similarly cruising around looking for Landys on drives and also wanting to convince owners to buy security gear - whether it can be bypassed or not.
And this is much more fun than rocket science.