Matthew Lebsack was fired by US rail giant Union Pacific after the incident in November 2016, but a federal appeals court has reluctantly reinstated him.

Mr Lebsack, an 18-year-veteran employee, had “defecated on the connector between two cars, threw soiled toilet paper out of the window, and told his manager he left a ‘present’ for him”.

The US Court of Appeals for the Eighth Circuit, upholding a district court ruling, said the courts were bound by the decision of an arbitration body called the National Rail Adjustment Board.

Circuit Judge Steven Grasz said: “We share the district court’s bewilderment at the Board’s conclusion that a company cannot fire someone for purposefully defecating on company property. Even so, we cannot review the merits.”