My son bought a cheap day return ticket yesterday from Epsom to
Potter's Bar. He bought it from the Southern machine at Epsom
station. The outward journey (Epsom-Vauxhall-Finsbury Pk-Potter's
Bar) was uneventful, but on the way back, the barrier at Vauxhall
Underground would not let him out. He showed his ticket to the
attendant, who said it was not valid for the tube journey -- though
she let him out without asking him to pay.

Looking at the NRES website, a CDR Epsom - Potter's Bar with a YP
railcard is £9.50, which is what he was charged. The website is
silent, so far as I can see, on the subject of whether that includes
the tube journey, though the attendant was correct in that his ticket
did not have the '+' symbol indicating that the tube is included.

I was under the impression that all cross-London tickets include the
tube segment, at least by default. Am I wrong? Or is the machine
just programmed wrongly? I am reasonably sure that the same machine
recently issued an Epsom - Cambridge return which included the tube,
and I have never seen it offer a 'tube or no tube' option.

There are no Underground barriers at Finsbury Park (my son says), but
his ticket did let him into the Underground at Vauxhall on the outward
journey. He mentioned this to the attendant who said yes, it will let
you in but not out -- which would seem to be strange advice, were it
not for the fact that it appears to be true.

Peter CS