In both attacks, either side of midnight on Sunday, youths threatened the driver and escaped with the cash tray.

In both cases, the CCTV video equipment was either missing or simply not plugged in.

Trouble first flared as a 289 bus neared the junction of Lower Addiscombe Road and Woodside Court Road at 10.05pm.

Fifteen youths who had got on earlier at Valley Park steamed through the single-decker bus, grabbing the driver's cash box and running off towards Blackhorse Lane.

The bus did not have a shield separating the driver's compartment or video recording equipment.

Then just after midnight, the driver of a double-decker route 60 bus was attacked by three teenagers as he drove through central Croydon.

They pulled open his internal door and started punching the 22-year-old driver in the face, before grabbing the cash tray and escaping.

According to the police, the video recording equipment on the bus was a dummy system.

A spokesman for Arriva promised an immediate safety review, saying it was normal practice to have dummy cameras on some buses.

"This sort of incident is awful and we will certainly be reviewing the situation in Croydon," she said.

"While a lot of our buses have CCTV cameras and hidden cameras some do have dummy cameras in place.

"If there are continuing problems we would look at bringing in special buses with hidden cameras onto routes."

Anyone who witnessed the attacks should call DC Darren Harber at South Norwood Robbery Squad on 020 8768 1212.