The 'West London Orbital Railway' - from Hounslow, via Old Oak Common, Harlesden and Neasden, towards Hendon or Cricklewood (or both!)

The 'turn south at Cricklewood' option

The 'turn north at Cricklewood' option

2017-09 West London Alliance - 7. West London Orbital Rail Progress and Next Steps by scribdstorage on Scribd

(Old Oak Common HS2 station is roughly
where the 'North London Line' wording is.)