Haggis!

A little unseasonal, but as it's been pouring down all day and currently feels like January, why not?

You'll need:

one haggis (preferably MacSween's, but in an emergency any will do. You can even get vegetarian ones if you're squeamish)
potatoes/swede, if you like the neaps and tatties combo, otherwise just some boiled potatoes will do fine
veg - we had carrots and peas today, but anything solidly British (none of this Mediterranean nonsense) will do
Nigel Slater's esteemed onion gravy (although haggis is also surprisingly good with brown sauce)

Stick the oven on at around 190 degrees C. (Don't even think of boiling a haggis - roasting them makes them much fluffier and nicer.) Wrap your haggis in foil, and put in a roasting tin, with a centimetre or two of water in the bottom. Bung in the oven for about 90 minutes until it's piping hot (although if it comes out piping Scotland the Brave, run for the hills).

If it's Burns Night (25 January), you'll need to spout a bit of poetry (the Address to a Haggis), and then go in for the kill with a large knife. If it's a wet Friday night in Gateshead in September, you're off the hook.

UPDATE: More haggis recipes here, when you get bored with the traditional one.