On 16 Aug, 17:11, "John Salmon" wrote:
"Martyn Dawe" wrote

I believe these trains are based at Ilford does this mean that at
the
start of service they have to come into Liverpool street and out to
cross the lines to get to the chingford side. where does this
happen ?

At Liverpool Street, platforms 1 to 4 are accessible from/to the
suburban lines only, platforms 5 to 10 suburbans or mains, 11 & 12
mains only, 13 & 14 mains or 'electrics', 15 to 18 'electric' lines
only. There are various places trains can cross e.g. around Bethnal
Green, or between the electric and the main lines further out.

While allocated to Ilford Depot for maintenance purposes, the stock
used on the Chingford line would generally be stabled at Chingford
Carriage Sidings - must be space for a few dozen units there. Same as
stock stabled at, for example, Bishops Stortford would form early/late
trains on the Cambridge line. The diagramming of the stock on the
'One' netwrok is such that many units do swap routes during the day
and may well end up at a different stabling location.

As John says there are various crossovers between Liverpool Street and
Bethnal Green (and at Hackney, Stratford etc) that allow a train to
depart/arrive any platform at Liverpool Street to/from any
destination. Obviously it would cause chaos on the approaches if you
tried to bring a Southend line train into platform 2, or send an
Enfield out from platform 16 in the daytime, so trains generally
depart from the platform groupings in John's post.

However, until around 1980-something, the west side of Liverpool
Street (platforms 1-8) was closed on Sundays IIRC. All trains then
used the long mainline platforms 9/10 (as was) or the east side
platforms 11-18. Occasionally now even during late-night or Sunday
engineering work Chingford trains might depart from east side
platforms, generally 11/12/13 to minimise conflicts.