Thousands of commuters were left stranded on the roads this morning as bus drivers mounted another 24 hour strike.
The protest by members of trade union Unite involves one of Ealing's main bus operators and was due to start at 3am.
First Buses and Metroline passengers are being urged to make alternative travel arrangements and to check updates regularly for affected routes.
Adrian Jones, managing director for First Buses London, said: "The union is intent on dragging further bus companies into strikes in pursuit of its fruitless bid to standardise conditions of work and pay in all companies, and we understand other companies will be affected.
"Bus drivers who have participated in the three previous days of strike action have already lost a significant amount of pay and this will not be recouped.
"These are difficult times for everyone and I hope the union will be ready to meet to discuss a settlement without leading to further loss of pay and damage to the company.
"We will do all we can to minimise disruption to services."
Only two bus routes in Ealing will be unaffected - the 112 and 65.
Busy Metroline services including the 297, E2 and E8 and First Buses routes 207, N207, 427, 607, E3, E7 and E9 have ground to a halt.