A robber escaped with tens of thousands of pounds after barging into a security guard outside an Oxford bank yesterday.

The robbery outside Lloyds TSB in Banbury Road happened at about 10am.

A Securicor guard was delivering money to the bank when the man barged into him He grabbed the cash box and ran off along Stratfield Road towards Woodstock Road.

Police are investigating whether the incident was captured on the bank's external CCTV system. It is not clear whether it was an opportunistic theft or planned.

The raid happened only a short distance from where masked gunmen stole thousands of pounds from Group 4 Securicor (G4S) guards four months ago.

The thief, described as black and in his early 20s, had dark stubble and was wearing a black hooded top with a short sleeved high visibility jacket.

Police are appealing for witnesses to come forward.

Det Insp Kev Elkins, of Thames Valley Police, said last night: "We are asking people to look out for this man and contact police if anyone sees him. He ran off on foot with the cash box, which is grey, and about 2ft long and 1ft wide.

"The Securicor guard was left uninjured by the robbery, but it was a distressing incident and we will not tolerate this type of crime."

No weapon was used, but the guard was left shaken by the incident.

A G4S spokesman said the cash box had a "unique forensic anti-theft system incorporated into all cashboxes used by G4S couriers".

She added: "As a result, criminals who break into a G4S cash box will become contaminated by SmartWater, which cannot be seen by the naked eye.

"SmartWater currently has a 100 per cent conviction rate when used as evidence in a court of law."

Anyone with information about the theft should call 08458 505505, or Crimestoppers on 0800 555111.