A bus driver has been left traumatised after an unknown liquid was thrown on him in an attack in High Wycombe.

CCTV images have been released of a woman police believe may have “key information” about the assault, which happened in Frogmoor.

A woman got onto the number 1 bus in Hazlemere and showed an out-of-date pass to the driver at 11.50am on June 12.

When the driver challenged the woman, she became verbally abusive and carried on into the bus, sitting down in a seat.

The driver refused to move until she paid for her ticket, prompting a member of the public to offer to pay for her ticket.

When the bus stopped at Frogmoor, the woman walked towards the door and, on her way out, threw the contents of her water bottle over the driver.

Investigating officer PC Karen Collet, based at High Wycombe police station, said: “I am appealing for the woman in these CCTV images, or anyone who recognises her, to come forward as I believe she has information that could prove vital to this investigation.

“The victim was left traumatised by the incident and they weren’t sure at first whether it was just water that had been thrown.”

Anyone who witnessed the incident or recognises the woman in the pictures is being urged to call 101 quoting reference number 43180177664, or contact Crimestoppers anonymously on 0800 555 111.