A reduced timetable has been published, showing that just 11% of rail services will run today, with some areas having no trains.
Delegates travelling to the Conservative Party conference this weekend and runners and spectators trying to get into London in time for the start of the marathon on Sunday are likely to be frustrated by the strike.Mick Whelan, general secretary of Aslef, said his members are increasingly angry at the lack of progress in the long-running dispute over pay, jobs and conditions.
Another strike by Aslef will be held on Wednesday, while RMT members will walk out again on 8 October, and again on 10 October in Scotland. "It is particularly disheartening that this weekend's strike will hit the plans of thousands of runners who have trained for months to take part in the iconic London Marathon," he said.