It's a while since I saw 'The Bargee' but as you'll probably know that in the movie Harry H Corbett & Ronnie Barker work a stretch of the Grand Union Canal. Hemel Hempstead is one of many towns through which it passes.
In the movie when asked how he got the name Hemel Harry H Corbett confirms that it was because he was born on the canal at Hemel Hempstead. To this Ronnie Barker pipes up and says that it was a good thing he wasn't born at Berkhamsted!
Bobj (Hemel Hempstead resident)