In message , marcb
writes

Does the Met line run to Watford on Saturday? I can't work this out on
the TFL site.

Yes (from Baker Street).

If not, what's the fastest way of getting there from the City area (ie
Moorgate)?

There's no tube service between the city and Baker Street this weekend.
Circle/Bakerloo would get you to Baker Street, but mainline from Euston
is almost always going to be faster (14 mins on the fastest service).

--
Paul Terry