Colin McKenzie writes
At Marylebone, in the morning peak, most passengers will be going
down rather than up, therefore - with an up escalator service still
having to be maintained - all these passengers will have to use
the fixed staircase. Presumably it is considered that this volume
of passengers using a narrow staircase would be unsafe.

Especially as at Marylebone passengers will reach the tube station in
lumps rather than evenly spaced - it's a main line terminus with rather
infrequent trains.

This may not apply at Moorgate because more of the passengers get off
before the terminus.

It doesn't apply at Moorgate as you go *down* the escalator to reach the
WAGN platform - so it's the up escalator crowd who arrive in lumps.
Passengers travelling down arrive in dribs and drabs - *and* they have
an alternative route to the WAGN platform (via the Northern line
platform for example).

--
Dave