A bungling robber ran straight into a parked van when the underpants he was using as a mask fell over his eyes, a court heard.
Jason Keogh used a loaded antique French revolver to threaten a terrified G4S worker collecting money from the Morrison's on Aldermans Hill, in Palmers Green, north London.
Using a pair of briefs as a disguise, 44-year-old Keogh attempted to grab the cash box.
When the guard resisted and grabbed Keogh's jumper, the bandit pulled the 140-year-old firearm from his tracksuit bottoms.
As he made off, the security worker went back to his van to call 999 and activate the automatic dye protection system inside the box which contained £22,405.
Michael Stradling, representing Keogh told the Old Bailey: "This all descended into a bit of a farce."
The robber was caught on CCTV pacing up and down an alleyway close to the supermarket for about an hour before the stick-up.