Finally, I could take no more. I caved, and bought this online:
A first edition, first impression, with the magic number '1' in the indicia. But not only that. There's also this:
Yes, it's a signed edition. I didn't realise Le Carre signed books as Le Carre, which is of course a pen name (his real name is David Cornwell). But apparently he does. Anyway, luckily I managed to find a copy from an Amazon Marketplace dealer – the same fellow behind the Firsts in Print website, I think – that only set me back the full price of the book, which, considering signed true firsts are going for all sorts of daft prices on eBay, could've been a lot worse. And even though Our Kind of Traitor falls firmly under Roly's broad brush assessment of later Le Carre, it's still a new Le Carre, and when I've been on such a Le Carre kick of late, it seems to churlish not to get his new one. So I have.