The CCTV clip shows a man come up behind a security guard at HSBC in Dewsbury and make a grab for money being removed from a cashbox.
Police released footage of the January 6 robbery this week in the hope of finding new leads.
Det Con Richard Proud, of Dewsbury CID, said: “The CCTV we are releasing shows that this robbery took place in a busy bank at a busy time of the day. It shows how the suspect went into the bank before the security guard, who he then attacks before running off with the stolen money.
“While the guard wasn’t injured, this was a serious crime and we hope that the footage jogs somebody’s memory or compels someone with information to come forward.”
After snatching the cash at around 2.15pm, the man joined two male accomplices in a silver coloured car, thought to be a VW Passat, which sped off from Bond Street.
It made a U-turn outside Dewsbury train station where it collided with a red car, causing minor damage before setting off once more.
The car, which was stolen from Huddersfield on December 30, was later found abandoned in the Meadow Lane area of Dewsbury.
The suspect pictured in the footage is described as a mixed race or Asian man, 6ft 3ins to 6ft 4ins tall and well built. He wore a dark coloured hooded top, a green military-style short jacket, dark trousers and shoes, and a light coloured baseball cap.
Phone Dewsbury CID via 0845 6060606 or Crimestoppers anonymously on 0800 555 111.