All the London railway stations :
Underground lines : Northern, National Rail First Capital Connect
I visited Kentish Town station on the Northern line in June 2019, and the station is seriously NOT accessible. There are initially 20 stairs from the southbound platform, then a very long lift. Escalator access between street and platform to northbound platform only, towards High Barnet, is apparently with no stairs.
Kentish Town station
Kentish Town stairs (22) from the platform to the elevator
Kentish Town elevator
Accessibility friendly : Kentish Town is not accessible to wheelchair users due to many stairs, or escalators, between the platforms and street level. There area also stairs and escalators between platforms and train lines.
General description : See wiki
More comment : British Rail Map & Guide