Travellers on Virgin CrossCountry trains faced further disruption yesterday because of a third one-day strike.
The firm's guards were holding another 24-hour walkout in a dispute over pay and conditions for Sunday working.
Virgin CrossCountry, which operates between Penzance and Aberdeen through Birmingham, said the industrial action would have less impact than engineering works that were being carried yesterday as well.
The RMT union vowed that its 370 members employed by the company would continue the industrial action until management agreed to their demands.
The union's organiser in the Midlands, Ken Usher, claimed a deal agreed with the management had been blocked by the board. He said: "In our last pay deal, rates from Monday to Saturday went up.
"But it didn't go up for Sunday pay, which had always been 17.4 per cent higher than rates for the rest of the week.
"So we want that differential restored."
Virgin CrossCountry said its pay rates were among the most generous in the industry, at more than £13 an hour.
The company said it would run at least 123 trains, the same number as operated during the New Year's Day strike by the guards.
During the first walkout, just 91 out of its 150 trains were in service, said a Virgin spokesman, Allan McLean.