An employment tribunal in Watford ruled that Jonathan Richardson’s pranks were humorous and not intended to cause distress.

The driver, 48, left the remains for a colleague to find after she said spiders made her “squeamish”.

He was exonerated by the tribunal despite the fact the woman was distressed by the incident and the fact he followed it up by leaving snakeskin for her to find – after she had threatened to report him.

Rail bosses found him guilty of bullying and dismissed him.

Richardson said he had not realised that his colleague, Driver A, was genuinely upset.

Matthew Hunt, the judge, said all parties involved “appreciated what a prank was. Its purpose is to elicit a short-lived reaction of shock or surprise, followed by some sort of feeling of relief and good humour.”