Eaton House, a London prep school catering for children aged from two to 13, has warned parents that two men in a dark grey van attempted to abduct children last week during Halloween, The Daily Telegraph has reported.

The school’s principal Sarah Segrave urged parents to be “vigilant and report any concerning situations to the police immediately” and asking if they were comfortable with their children making their own way home unsupervised.

Eaton House has schools in Belgravia and Clapham. The reported incident took place at around 7.30pm near Clapham Junction in south London.

A Metropolitan Police spokesperson said: “We are aware of online reports relating to a suspicious incident on Tuesday, 31 October, when two men were seen in the area of Nansen Road and Forthbridge Road, Clapham, trying to offer sweets to children who were out ‘trick or treating’.

“These concerns were reported to the police on the day and an officer attended the scene.

“An investigation into this matter has been launched led by South West BCU CID and enquiries are ongoing.

Chief Inspector David Lee commented: “We understand that these reports must be very distressing for parents and members of the local community.

“Trick or treating should be a fun activity and the fact that children were targeted whilst they were out enjoying themselves is very concerning.

“I would like to reassure the community that we are looking into this matter and officers are working hard to find the two men concerned.”