Thanks for correcting my confusion. The dene connection sounds abot right as there are two valleys there. One in which the smalll village of Batford is situated and as you go up the hill from batford you crest and go over into Harpenden. It's interesting that the harpen- part means army way, though watling street (the A1 as is) does actually go through Harpenden but is a few miles west of it. Another thing, on the edge of one of the roughest council estates in Luton there is an old Iron age fort, for some reason it has survived all that the local trailbikers could throw at it (at least that was until 6 years ago when I left the UK). The estate is called Marsh Farm and the sources of the river Lea are quite close to where, the earthworks are. The area adjacent is called Leagrave.