I thought the plans were originally for services on the High Wycombe line
to
use Paddington instead of Marylebone and for serices on the Aylesbury line
to use Baker Street and further stations in central London instead of
Marylebone.

Which would involve running on single-track between Northolt Jctn and
Greenford Junction, plus Park Royal Branch Junction and Old Oak West
Junction, plus running along a crowded section of line into a busy station,
not fitting in with 1 TOC per terminal policy. Stupid idea whoever thought
of it
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