Found 18th Nov 2012
No idea if this is national or not, but seen in Tesco Corstorphine (Edinburgh) Calvin Klein boxers for £10, for 3 pairs. that's £3.33 each pair. They had a whole box full of them, next to the pet food isle. (no idea why there). Most of the sizes were XL but i did see an M and L too so its an arrange of sizes.