Paul Terry wrote:

It should produce a more robust service if the trains *do* continue around
the circle, after a suitable wait... that way problems which affect the
clockwise can't affect the anti and vice versa.

I don't think that the Orbirail project will ever run a fully circular
service, because of the potential for serious delays (like the circle line
but infinitely worse).

Maybe not a complete circular service, but some through services running
across Clapham Junction would have clear attractions, especially as it would
reduce the interchange pressure and give passengers a better indication of
how long it will take to get to their destination. Back to back terminuses
aren't as attractive for passengers - look at buses where there are mancy
cases of two services on what is basically a single long route overlapping
rather than having all the changeover in one place.

That said I'm not sure where the natural terminuses for a reasonable service
running across Clapham are.