All the London railway stations :
I visited Highgate station on the Northern line in June 2019, and the station is seriously NOT accessible. There are no raised platforms allowing step-free from train to platform. You can swap from the northern to southern platforms easily.
To exit the station, there is an escalator (118 stairs) to the ticket hall. Then either 16 steps to the Priory road exit, or apparently an escalator to the Archway road exit. I did not see this escalator and climbed 51 steps! Signposting could be a lot better.
Underground lines : Northern
Accessibility friendly : Highgate is not accessible to wheelchair users due to stairs or escalators between the platform and street level.