Colin Chapman was reportedly preparing to drive a train from Edinburgh to Glasgow when he was caught. Picture: Jane Barlow

Colin Chapman, 54, was said to have been caught at Waverley Station before the late night service departed on May 25.

Edinburgh Sheriff Court heard yesterday that he provided a blood sample of 174 milligrams of alcohol in 100 millilitres of blood. Railway regulations stipulate a maximum reading of 20mg per 100ml.

The court heard that Chapman, of Milngavie, had resigned as a train driver following his arrest. Sentence has been deferred until next month for reports.

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A spokesman for ScotRail said following the case: “This was an extremely rare occurrence.