Police used borrowed bikes to chase suspects after a group of masked youths threatened a boy.

Hertfordshire Constabulary says the boy was threatened near the Mill End Sports and Social Club by a group of youths using bandanas to cover their faces on Saturday, March 7 at 4.45pm.

It was alleged that they had a knife, though no weapons were found.

The victims’ trainers had been stolen.

Two suspects were arrested by officers from the Three Rivers neighbourhood team.

Two more suspects were later seen by police, who chased one of them for a mile along the canal towpath towards Cassiobury Park.

Police were then lent bikes by a canal boat owner.

A third suspect was later arrested.

Three 16-year-old teenagers have been arrested on suspicion of robbery.

They have been released under investigation while enquiries continue.