In article , Recliner
writes
I forgot about T4. It's at 71.53 (so more than 2 km further than T5) but
that's via T2&3. Going direct from Hatton Cross it would be at 66.83.

As it's a one-way loop, which would be the 'official' direction to measure?

It's measured anti-clockwise, so if there are any posts in the tunnels
that's the way they go.

I suppose, if all distances are measured from Ongar, you'd measure the
direct route. Would that be measured assuming switches at Mile End and
Hammersmith?

Mile End and Barons Court.

Transfers are always done somewhere where the lines are parallel or on
the same track so you don't need to identify a specific place to
transfer.

--
Clive D.W. Feather