Me and by brother got one when i must of been about 12, anyway we were going up to Scotland on the train trying to solve it...during which a guy sat next to us said "pass it here, i can do it".

Obviously my brother and I didn't believe him, nor did my parents, but we let him try anyway. About a minute later he was done. 7 Years on I'm yet to solve it (although I've never looked at a guide, that ruins the fun :P)