Marty wrote:

Forgive my ignorance - hard to keep up from 12,000 km away, but is
the "New North" line out from Old Oak Common to Northolt Jcn still
used by any passenger trains from Paddington? ISTR the line was
singled in part some years ago, but that there was still the
occasional train from Padd to (presumably) Birmingham

The Birmingham Direct line, between Old Oak West Junction and Northolt
Junction, is still used occassionally for freight workings,
parliamentary trains, ECS and diverted passenger trains. When the link
line from Neasden to Northolt is closed and Chiltern trains cannot
reach Marylebone, the Direct line is used to run Chiltern services to
Birmingham from Paddington.

The line is single between Northolt Junction and Greenford West
Junction, double thence to Park Royal West Junction and single to Old
Oak West Junction. Linespeeds are appalling along this stretch, with 40
being the average for a route that was once 90.

Rumours once placed this line at the center of the Crossrail route to
High Wycombe.