But the walk-out looks certain to go ahead, and in the absence of moves by BR to reopen negotiations on its "final" 3 per cent pay offer, the dispute is set to widen to the London Underground. Around 2,000 tube drivers are expected to give an "overwhelming" vote in support of industrial action when their ballot is counted on Wednesday. They would then be called out on 27 July, along with members of the main rail union RMT.
Aslef's third one-day stoppage on British Rail has already been set for that date, and with both rail and Underground systems disrupted, London faces its most chaotic strike day for years.
To Labour's dismay, this is also polling day in the Littleborough and Saddleworth by-election, where Tony Blair is staking much of his personal authority on a win for his modernised party.
BR's efforts over the weekend to talk drivers out of striking have been made more difficult by the introduction of a new penalty points disciplinary system, which the union says is a "bully's charter" for managers.
Apart from a long list of driving offences, such as speeding, overrunning the platform and not sounding the horn correctly, the system includes what the union regards as social offences, such as having bulging pockets. Being known as a heavy drinker carries a particularly high penalty. Drivers who score too high are subject to monitoring and risk being taken off the footplate.
Lew Adams, general secretary of Aslef, said: "Threats of discipline come thick and fast if you've a moustache, a beard, a tattoo or an earring. Managers are trying to prove they are in charge so that the industry is ready for privatisation."
He challenged British Rail chairman John Welsby to debate with him the pounds 72,000 bonus he is expected to receive, by comparison with the pounds 200-a- year increase for drivers. "We are available for negotiation anywhere, at any time," he added.