THREE men threatened two security guards with a gun as they filled a cashpoint at a Tesco store in South Harrow on Monday.
The gang approached the guards as they started to fill the machine outside the Shaftesbury Circle store at about 10.50am.
One man entered the small cupboard area the guards were working in brandishing the weapon and demanded they lie face down on the floor.
The guard told police two others then entered the room and the group ran off with a cash box which had a small amount of money in.
The gang then drove off in a car along Shaftesbury Avenue towards The Ridgeway.
Detective Constable David Reed of Finchley Flying Squad asked anyone who had seen the incident or regularly uses the parade of shops to come forward.
The gunman was white, aged 25 to 30, around 6ft 2ins tall with a shaven head wearing a high visibility jacket.
The other two suspects were both described as tall black men, one wearing a dark hooded top, black trousers and a scarf covering his face, and the other had a black cap and hooded top with pockmarked skin.
Anyone with information can call the incident room on 0208 358 1751, or Crimestoppers anonymously on 0800 555 111.
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