Police are searching for a red-handed robber who threatened a security van driver with a knife and stole cash.

The armed robber would have been left covered in security dye after opening the box, triggering the red liquid to disperse, and leaving it discarded near Waverley Crescent in Brighton.

Dye had covered the area near where the box was discovered. All the cash, an undisclosed amount, had been taken.

The robbery took place yesterday Thurs, at 12.20pm, on the forecourt of the Downsway BP Service Station in Ditchling Road, Brighton.

The robber approached one of two Securitas guards who were delivering cash to the garage and said: "Hand over the box and the keys. If you don't hand them over I'll stab you."

People filling up their cars with petrol watched in shock as the robber approached the driver of the van.

The security van driver handed over the box. Nobody was hurt in the raid.

After the robbery the man drove away in a small, silver hatchback car and went north up Ditchling Road towards the Hollingdean area.

The cash box was found shortly afterwards.

The garage manager, who didn't want to give her full name but said she was called Donna, told The Argus it was clear the robber was targeting the security van and not the service station.

She said: "He was going back to his van to pick up a box of money.

"Me and my supervisor had gone to take the service station cash to the bank. When we got back the forecourt was covered in police.

"One of our cashiers was in the shop at the time but I don't believe they saw anything.

"We had to shut for about four hours while the police carried out their work.

"The guard wasn't hurt but he was badly shaken. He stayed here for about 20 minutes afterwards and then went to the police station to make a statement."

The knife is described as a "lock knife" type of weapon with a five inch blade.

Officers were yesterday trawling through CCTV footage and making door-to-door enquiries around the Ditchling Road and Waverley Road areas.

The robber is described as white, in his mid 30s, about 5ft 8ins tall, with a medium build and short, dark hair.

He was wearing a black suede jacket, blue jeans and had a Liverpool accent.

A Sussex Police spokeswoman said: "We have spoken to a number of eyewitnesses but are appealing for any other members of the public to get in touch if they know anything."

Anyone who witnessed the incident is asked to contact Detective Sergeant Mick Richards at Brighton CID on 0845 60 70 999 or Crimestoppers on 0800 555 111.