Unrelated, but I've just found out Watford is in London, well I never.... I thought it was much further up than that.
Watford is in Hertfordshire sweetpea - someone's been fibbing to you.
Ha ha...proof I can't read a map, I swear I saw it in London.....
But I do know where East Angular is! 
Hatch End (London Borough of Harrow) is 3 train stops away so nearly but not quite 
BTW most Americans can't point to Canada on a map so it could be a good deal worse 
Watford is inside the M25 and on the end of a tube line, so for the non-London initiated it probably does look like it's in London. They also (somehow) manage to call Luton airport "London Luton" which would suggest that Watford, St Albans, Hemel Hempstead, Welwyn and Luton are all in London too.