Thames Valley Police is appealing for witnesses to a robbery in Milton Keynes on Saturday.
At around 11.15am, the driver of a silver Vauxhall Vectra was parked in Kellan Drive in Fishermead. He was completing paperwork when two men on bikes tried to get in to his car.
The driver was hit and the offenders smashed the front passenger window before taking an envelope that contained around £500. They rode off along Kellan Drive before turning onto a Redway.
The offenders are both white and in their mid twenties. One man was wearing a black hooded top and was riding a BMX type bike which was light in colour, with chrome stunt pegs on the back. The other offender was wearing bright yellow and green trainers and rode a mountain bike with disc brakes and rear suspension.
Anyone with any information about the robbery should call police on 0854 8 505 505 or Crimestoppers on 0800 555 111.