lonelytraveller wrote:

What about a diveunder under the mainline at watford junction, and
then taking over the disused rickmansworth branch, and thence to
chalfont & latimer - to take over the chesham branch of the met?

Why on earth do that? It's a tram - it doesn't have the same constraints on
gradient and curvature as a train. If you're going to extend it in what is
largely countryside, you can put it pretty much anywhere, and former railway
alignments are not much more useful than anywhere else. Extending the other
end to Redbourn, Luton Airport Parkway and Luton Airport Terminal is the
same distance as your proposal, probably cheaper and about a million times
more useful.

--
We are the Strasbourg. Referendum is futile.