This is (as far as I know) a strictly British usage.
We, in the Former North American Colonies, do not ever use that word in that way.
I rather like it, but it will get you funny looks here.
I get funny looks everywhere pal :eek!:.
Hows this for a nice put-down: 'you are a right fruit-cake'. Others of a similar hard to understand nature if you are not native to these shores are 'soft as a brush' meaning the same as 'right fruit cake' and meant to express someone is a bit silly without being really insulting.
But using words in different ways than the traditional is surely not confined to the UK. Didn't the use of the word 'hot' to mean fashionable, and not having a high temperature, come from the States, and didn't the next generation rebel against this by using the word 'cool' to mean the same thing? Over here, at one point, 'wicked' meant 'good' and indeed for a time 'bad' meant 'good' too.
However this all might qualify as hijacking a thread so I will 'pipe down' and 'shut my cake-hole'.
Lee