In reply to Nic:
I've never been asked for it having hired cars throughout Mainland Europe, Southern Africa, Iceland, Malta, and the USA.
But I always get asked to produce it when hiring in the UK.
I always take it with me though because it would be sod's law that if I didn't I'd be asked. So my advice would be take it in case - its no big deal and I've folded mine up so that it lives in my wallet along with the plastic part.