Lewis Hamilton, from Chelmsford in Essex, threatened an associate manager with a six-inch knife while she was counting up the day's takings from the Trading Post pub, where the robber used to work, a court heard.
His former employer, Holly McDonald, recognised Hamilton when the jacket and scarf that was covering his face slipped down. The court was told he then told Ms McDonald: "Don't worry, I am only joking."
He then told her that he had come to return his uniform, despite not having it with him.
Hamilton had been working at the pub for just 13 days when he was sacked. The pub had discovered that he had lied in his interview for the position by saying that he had left his previous job voluntarily, but he had in fact been fired for failing to pay for a food tab.
Basildon Crown Court heard how Hamilton broke in to the pub through a fire exit and lurked outside the office, while Ms McDonald cashed up.
Hamilton was given a two years prison sentence after he admitted to the aggravated burglary, which happened in October.
Meanwhile, a similar incident occurred earlier this year on 5 November when David McGreavy, 24, was caught hanging off a 20ft rope while trying to break into a room on the fourth floor of Blackpool's Hilton Hotel.
McGreavy, of Blackpool, claimed that he was simply trying to swing into his girlfriend's bedroom, however he was equipped with gloves and a pillowcase.
McGreavy later admitted to going to the hotel equipped for theft when the case was referred to Preston Crown Court.
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