Answer: A laptop keyboard.
I've been unable to do a lot of work for the past hour or so after spilling a tiny amount of coffee over my laptop keyboard. Fortunately I don't take sugar as Steve assured me that was a known killer. I dried it straight away, but of course, most keys weren't working. After spending 20 minutes working out how to take the cover off to be able to get to the screws holding the keyboard in place, head for the shower. 1 minute on a luke-warm wash, towel dry, hairdryer on cool with a full blast for another 5 minutes and leave to bake in the sun for another 10 while reading a chapter of Harry Potter and it came back to life. Phew. All except, though, the most important key - Enter. I don't have a USB keyboard to hand here, but the beauty of running Windows Server on my laptop is that at least I can terminal service in to it over the network to continue working. Strange though, half an hour later,
I've got a replacement on order anyway to be on the safe side - you never know quite how much gunk may still remain there. At least all the crumbs and chocolate flakes aren't there.
PS: Best not answer my original question (unless it's safe to publish).....