John Gordon, 57, saw off the terrifying intruder after the would-be thief burst into his post office in Crossgates, Fife.
The robber – disguised by a balaclava – thrust a bag over the counter and demanded that John filled it with cash.
But brave John twice refused, sending the desperado packing, before calmly calling police and getting back to serving customers.
John – who has run the small village shop with wife Sandra for 11 years – said: “My only concern was that there was a customer with their young grandchild in the store at the time.
“Nothing like this has ever happened before, I still love the job and will keep going. I’m just glad it was me in the shop at the time, rather than Sandra
“I don’t think of myself as a hero, I just reacted. I get more embarrassed with people asking me about it than anything.
“I didn’t know if he had any weapons and I was just hoping that he would go away.
“It didn’t strike me what I had done until I was watching it back on the CCTV with the police, at the time I didn’t think about it.”
John was serving customers at the shop in the town’s Main Street when the raider burst in just after 4pm on Monday afternoon.
He said: “I was just serving a couple of customers and this boy just walked through the door and up to the counter. I noticed he had a mask on. He pushed a plastic bag through the counter and said ‘Give me the money’, I can’t remember the exact words he used.
“I pushed the bag back through and said ‘Sorry, I’m not giving you any money’.
“He pushed the bag back through and said ‘I’m asking you politely for the money’, and I pushed it back to him and said ‘I’m telling you politely you’re not getting the money’.
“He just ran out the door and I went to the side door to watch him before I called the police.
“It was not until he left that I thought about what had happened. You just don’t expect anyone to try to rob you, it was surreal.”
John – from Methil – had six-year-old golden retriever Bailey in the shop with him at the time, but admitted his beloved pet was not much use as a watchdog.
He said: “Bailey is with me six days a week and everyone was asking if he helped and even the police were asking what sort of guard dog he is – I just asked if they were joking.
“I don’t think he woke up during the whole time.”
Police are now hunting the bungling burglar and are appealing for witnesses to come forward.
Detective Inspector Derek McEwen of Fife Constabulary said: “The man was wearing a blue/grey jacket and had a dark tammy or balaclava on at the time.
“Witnesses have described how the man left the post office, crossed over at a nearby traffic light junction and then ran south on Dunfermline Road, away from the centre of the village.”
John said he was unable to describe the man because of the disguise but said he was wearing grey trousers and was between 5’10’’ and 6’ tall.