Watch: What days in December will trains be disrupted?
Members of the Aslef union have started nine days of strike action, due to run until 9 December, as part of a long-running dispute over pay.
The industrial action will affect train companies on a rolling basis, and the Aslef union has also imposed an overtime ban.
Many of the affected operators are expected to run no services at all on strike days, and travelling on the day before or after strike days might also be hit.
Rail Minister Huw Merriman said the strike action would cause "more misery for passengers and the hospitality sector this festive period".
BBC London's Tom Edwards outlines what the December strikes could mean for you.
