Toy guns, picnic knives and builders’ tools were some of the forbidden items seized at Parliament Hill Lido last year after security was increased following a brawl in which two teenagers were stabbed in 2012.

The blades and other banned objects include a blue plastic handgun taken from people attempting to enter the lido by officers stationed at its entrance.

Details of the items were released as part of a review of the Hampstead Heath Constabulary’s work in 2013 which was published last week.

Richard Gentry, head of the constabulary, said: “Sometimes it’s just people going in with picnics, who will take sharp knives to cut up bits of cheese.

“We also took a Stanley knife off a builder who had been working on a job somewhere and wanted to have a dip.

“We recover the items from individuals and dispose of them accordingly. It’s about ensuring that the facility is safe and people using it are safe.”

The constabulary used a knife arch metal detector for the first time last year on hot days when the pool was busy.

It was introduced following the knifing of two boys inside the pool after a fight broke out in July 2012.

A 16-year-old boy was stabbed in the abdomen and a 19-year-old knifed in the buttocks.

The constabulary, which has two police sergeants and 10 constables, dealt with 1,290 incidents across the Heath last year.

These included a bomb scare in April that was triggered when a car containing gas cylinders filled with used vegetable oil was left overnight.

“The owner of the car was going to make his own biodiesel,” Mr Gentry said.