100 Year Bonds

Apparently the UK is considering issuing 100 year sovereign debt bonds to lock in current low interest rates. Buttonwood pans the idea. Given the lessons of Vanished Kingdoms: The Rise and Fall of States and Nations, which I've been reading with great interest, it's hard to imagine a prudent investor being willing to commit to a 100 year bond even for a state as seemingly permanent as the UK. After all, as Buttonwood notes, Scotland could be out of there in three years. Who knows what 100 will bring?

On the other hand, the UK's national debt still includes consols dating back to the 1700s, which are effectively perpetual bonds. So maybe I'm being too pessimistic (or, OTOH, maybe the English were too optimistic back in those days).