A motorcycle gang robbed a stockbroker and his wife of watches worth £20,000 as they returned to their car after a family day out at Kenwood House in north London.

Two bikes drew up alongside the VW Tiguan at around 5pm last Saturday. Four men surrounded it and one smashed a hammer into the side of the car.

The father was forced to hand over his Hublot watch and his wife’s Rolex in what is believed to have been the latest in a series of such attacks in the Hampstead area.

Passers-by stayed with the couple, their son aged four and daughter, seven, until police arrived 30 minutes later, according to the 35-year-old father.

“I was strapping my son into the seat, when I heard this massive bang right near my head,” he said.

“My daughter screamed when she saw my wife getting upset. It was very threatening.

“One of them also wanted the bracelet that I bought my wife, but I spoke to him very calmly and said I couldn’t do that, because it was screwed on.

“If there was just one attacker, I would have taken him on. I wouldn’t have given him the watches — but there were four.”

The attack happened on the corner of Winnington Road and Ingram Avenue.

The father, from Hampstead Garden Suburb, said he thought the police “haven’t done enough” to secure the affluent area, after seven similar attacks, believed to be linked to the same gang.

“We heard they were breaking into houses but didn’t know these attacks were happening on the street. If we did, my wife and I wouldn’t have worn such expensive watches,” he added.

“We are now absolutely fine. I have insurance, these things happen. It could have been much worse. We’ve moved on and want to try to forget about it.”

A police spokesman said the force had “increased patrols in the area” as a result of recent attacks.