Euston-Watford DC line (now part of London Overground) to . Bakerloo services to Watford Junction were reduced in the 1960s and cut back in 1982 to .

Services as far as Harrow & Wealdstone were gradually restored from 1984, and in 1989 the present all-day service was instituted.

Stanmore branch

By the mid-1930s, the Metropolitan line was suffering from congestion caused by the limited capacity