Police are appealing for information to help trace two other men who fled in a green Vauxhall Astra following the incident at Stanley Hunt Jewellers in The Square, on Market Place, in Retford, at 4.40pm, on Saturday, September 29.
Staff were in the shop when three men allegedly took jewellery from the front window display.
One reportedly smashed the front door with a hammer and another threatened staff with a crowbar, according to police, while a third man allegedly armed with a baseball bat waited outside.
Police said a council worker who was putting away market stalls at the time allegedly tackled one man to the ground and detained him until police arrived. No one was hurt.
Officers also recovered some jewellery and a crowbar from the street outside the shop, according to police.
Detective Inspector Kim Binns, of Nottinghamshire Police, said: “I’d like to thank the brave member of the public who detained a man in connection with the incident, as well as the witnesses who have already come forward.”
Police are still appealing for anyone who was in the Market Place at the time and has not already spoken to police to call and for anyone who can help trace the green Vauxhall Astra.
Anyone with information is urged to call Nottinghamshire Police on 101, quoting incident number 666 of 29 September 2018.
Alternatively, they can call Crimestoppers anonymously on 0800 555 111.