An invitation from the grave

I had an intriguing item of mail today: a sealed envelope, posted to me in the regular way via Royal Mail, with a stamp on it. It was addressed to 'The Resident'. My full address was written on the envelope. It was meant for me (as the 'resident'), but it was also clear the sender didn't know my name. The name and address looked handwritten, in a neat but somehow rather juvenile hand - the work