The terrifying raid on Diamond Classic Gold Jewellers in Rotherham High Street took place at around 12.30pm on April 30 this year, after Shakeel Hussain approached the shop using a pair of crutches, rang the bell and asked to be let in.
Sheffield Crown Court heard how Hussain, 26, did not need the crutches and used them to appear vulnerable, a strategy that worked because the shopkeeper opened the door, and later told the police he did so because he 'felt sorry' for Hussain.
Declan Taylor, 21, and Lyle Copley, 22, and a third man, who has never been identified, ran into the shop as soon as the door was open.
"Immediately the three other men rushed in, and the court had heard that the unknown male leapt over the counter. You were all wearing masks, or something similar," Recorder Felicity Davies said, adding: "The shop owner was threatened with a knife and pushed backwards, he must have been terrified.
"Having seen that the shop owner could not defend himself or his shop or his stock, you tried to grab as much jewellery as you could."
Hussain exited the shop less than 30 seconds into the robbery. After his three masked accomplices left with the jewellery, Hussain remained in the vicinity and attempted to claim he had not been involved with the robbery.
Prosecutor, David Wain, told the court that the three men managed to get away with £2,500 of gold chains that have never been recovered.
They fled the scene in a stolen black Honda Civic. Thanks to a member of the public who made a note of the registration plate, police were able to trace the vehicle and following a short chase officers managed to arrest Copley, but Taylor and the third masked men were able to escape with the jewellery.
After being arrested, Copley was found to have 19 wraps of crack cocaine in his possession, worth an estimated £380.
At an earlier hearing Hussain, of of Bridge Close, Airmyn pleaded guilty to an offence of robbery, while Copley, of Kimberworth Park, Rotherham pleaded guilty to charges of robbery, threatening a person with an article with a blade or point and possession with intent to supply Class A drugs.
Taylor, of Cecil Avenue, Doncaster pleaded guilty to robbery and threatening a person with an article with a blade or point during Friday's sentencing hearing.
Defending Copley, Dermot Hughes, told the court that Copley's best point of mitigation was his early guilty pleas 'which in themselves express what is, in my submission, genuine remorse on his part'.
Assumpta O'Rourke, defending Hussain, said: "He accepts responsibility for the matter, and regrets agreeing to become involved with this matter."
In defence of Taylor, Ian Goldsack said the robbery had taken place on his 21st birthday and he had become involved after getting 'carried away' while drinking to celebrate.
Recorder Davies sentenced Taylor and Hussain to four-and-a-half years each for their part in the robbery, and sentenced Copley to eight years, after also taking his drug offence into consideration.