The company that owns Britain’s rail network still has further work to do to improve performance on the troubled west coast main line, rail regulators have said, despite a significant improvement in its performance.

Bill Emery, chief executive of the Office of Rail Regulation, was speaking after Network Rail, the network’s owner, announced that 89.6 per cent of services run by Virgin Trains, the operator worst hit by problems on the London-Glasgow line, arrived within 10 minutes of the scheduled time in August.