Train journeys on Virgin CrossCountry services were disrupted because of a one-day strike by guards on Sunday.
The strike is the third by Virgin Cross Country train guards
The guards held their third strike about payments for working on Sundays, the RMT union said.
A union organiser said the union was unhappy that a deal agreed with managers had been blocked by the board.
Virgin CrossCountry, which operates between Penzance and Aberdeen, said the strike had less impact than planned engineering works.
"The main impact on Sunday has been from the engineering work rather than from industrial action," a spokesman said.
He said the company had been able to offer a "comprehensive" service with trains travelling to cities such as Aberdeen, Edinburgh, Newcastle and Manchester.
He said 123 train were in service on Sunday, the same as last week, when services were also disrupted by industrial action.
The RMT union's organiser in the Midlands, Ken Usher, apologised for disruption to the travelling public, but said: "It's not a dispute that we wished to enter into anyway," adding that the union had hoped for a much earlier resolution.
"The company know exactly where we're prepared to negotiate," he continued.
"It needs them to take our offer and get back round the table. We remain open and available for talks."
Managers on duty
Managing director Chris Gibb said managers would be drafted in for the day.
He said customers were mostly unaware that there was a strike on and warned the union that he was "prepared to let this [dispute] go on indefinitely".
The RMT claims the introduction of a 35-hour week has led to its members losing money.
However the company says its pay rates are among the most generous in the industry, at over £13 an hour.