Eder Ruiz, 25, disguised himself with a black wig and joke teeth and even used electrical tape to resemble a fake beard and moustache before he carried out the raid at Burley in Wharfedale in May last year.
A jury at Bradford Crown Court heard that Ruiz collapsed on the floor and pretended to be ill in order to get Patricia Garforth to come from behind the secure area.
When she went to his aid, he pushed her aside and produced an imitation handgun – which may have been a water pistol – and shouted: “Open the safe. Open the safe.”
Mrs Garforth and her husband John, who had run the post office for 26 years, bravely tried to stop Ruiz taking cash from the till after he was told the safe was on a time-lock.
Ruiz got away with £1,800 but dropped a newspaper at the scene which was later found to have his fingerprints on it.
Mobile phone evidence also showed that he had been in the village an hour before the crime was committed.
He denied charges of robbery and possession of an imitation firearm but the jury took less than an hour to find him guilty at the end of his trial today.
Following his conviction, jury members were told Ruiz had a previous record which included house burglary and aggravated vehicle taking.
His barrister, Paul Hodgkinson, said he had been out of trouble for about six years and was studying at Manchester University for a business management degree.
He revealed that Ruiz had played for Leeds United but was let go by them at a young age and he suggested that had “clouded” his client’s adult life.
Mr Hodgkinson also said the prosecution case had been that Ruiz committed the robbery out of desperation after receiving numerous telephone calls about a variety of debts.
Ruiz, formerly of Otley, was sentenced to four years in jail for the robbery with an additional 12 months for possession of the imitation firearm.
“It is a very great sadness that your football career didn’t take off and it is a great sadness that you have placed in jeopardy your future education,” Recorder Taryn Turner told him.
Det Con Rob Stevens, of Bradford District CID, said: “This was an extremely frightening and traumatic experience for the victims, who have served their community for many years.
“Ruiz was a desperate and dangerous individual who was prepared to sort his personal debts out through violent means, and I hope his victims will take some comfort that he is now behind bars.
“Police are committed to protecting the communities of Bradford district and violent crimes such as robbery will not be tolerated.”
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