Is it possible that the improved timetable from later this month was
reliant on having some of the extra units in place. The fleet will be
growing from 6 x 2 car class 150s to 8 x 2 car class 172s. Even simple
replacement of class 150s with class 172s may give an increase in
capacity due to the longer vehicles (although there will be less seating
due to the 2+2 arrangement). Running more than a twenty minute frequency
looks difficult with the existing fleet size.

I don't think it did need more trains overall. The 15 minute interval
was only at the height of the peak. I think either the user group or
London Travelwatch showed a while back that you could create such a
timetable with adequate turnaround time to cater for the worst of the
peak with the existing fleet. I remember reading a document that set out
the scheduling and pathing issues.

Out of interest, what is it that's restricting the GOBLIN to 2 car
operation?

I live in Leyton and get the train every so often between here and Crouch
Hill (and would have used it much more often since moving here, but for
the weekend closures....) and most if not all of the intermediate
stations could easily deal with longer trains?

(Apologies if this is a well-worn question)