It was interesting hearing you guys discussing something I actually have expertise in. There was a lot I could say about your discussion on banknotes but I'll keep it to 10 or 20 points.

*The BoE will always old banknotes indefinitely. *Legal tender isn't what most people think it is (and there is no legal tender in Scotland). *Banknote designers have design rules based around manufacturing capability. As manufacturing technology gets better, so does the range of possible designs. *Commemorative limited run banknotes are actually extremely common and are often designed specifically to do well in the ISBN competition. *Complicated patterns can be a security feature, but they're not a particularly good one. It was almost certainly a design decision. Transparent windows are absolutely security features. *Plastic banknotes don't have watermarks. *American money is actually different from most other currencies as it has linen in addition to cotton. Most paper banknotes are cotton only.