That would be a good idea - thanks.

I don't mind the original error too much - without knowing the fine details of how redirections work, I can see that the very odd letter can get caught up incorrectly. And it was sheer bad luck that this should have happened to a moderately important letter, rather than one of the innumerable Christmas catalogues we have been getting. But the person I was speaking to did seem a little ... divvy, as you say.