Tom Anderson:
"on the Moorgate Welwyn Garden City / Hertford North routes contra peak
services (i.e. northbound until 0900 and southbound after 1600) are
only 2 tph."

Christ! How the hell does that work? Do most of the trains run ECS back
up north?

Clive Feather:
The peak arrivals run ECS back up to the northern termini to provide
another with-flow service.

How much time does that save over running in service?

12.5 minutes.
[Moorgate to WGC: 46 minutes in service, 33.5 minutes ECS.]

What if they ran back in service, but nonstop?
--
Mark Brader, Toronto,
"The recent explosion of tourism has ruined the
planet Arrakis for me forever." -- Spider Robinson