Armed police officers were patrolling the streets of Hampstead today after what was described as a ‘firearms incident’.

At around midday in Heath Hurst Road an officer spotted four people acting suspiciously and a gun was seen, the Ham&High understands. Three were arrested but one suspect escaped and is currently still at large.

As a police helicopter hovered over South End Green officers cordoned off both ends of the street while dog units searched nearby properties in the hunt for the escaped person.

A police spokeswoman said: “We are trying to trace a suspect described as about 16 years of age and wearing casual clothing. There is nothing to suggest this suspect is armed.”

The three people who have been arrested are currently being held in north London police stations.

Anyone with information about the incident should call police on 0300-123 1212.

Updates to follow.