A London bus driver discovered a caged monkey hidden in a laundry bag onboard his vehicle last week.

The marmoset is thought to have been dumped by its owner, prompting animal welfare officers to warn of further abandonments as a result of a recent change in the law surrounding the keeping of primates in England.

The driver of the number 302 bus, who has not been identified, found the terrified animal towards the end of the route from Mill Hill Broadway to Kensal Rise in north-west London, on Friday morning.

A mother had been trying to disembark with her child in a stroller but had been unable to pass as a large laundry bag was blocking the way, according to the Royal Society for the Prevention of Cruelty to Animals (RSPCA).

The charity’s chief inspector for London, Clare Dew, who is now investigating the case, said in a press release sent to CNN: “The driver came to help her and, as he pushed the bag out of the way, the monkey inside started chirping and jumping around. When he peered inside the bag he spotted the frightened marmoset.”