To some people, spending hours in Waterlow Park on the hottest day of the year might seem like a perfect idea – but the summer idyll turned into panic for about 30 people when they discovered they were locked in.

Marisha Ray was one of those who found herself trapped in the Highgate park at about 9.45pm.

She was returning home from doing some shopping, and went into the park through a gate by St Joseph's Church in Dartmouth Park Hill.

She then walked to the exit near Bisham Gardens, only to find it locked. Several groups were also still in the park, including a heavily pregnant woman.

Marisha, who is standing for the Lib Dems in the London Assembly elections next year, said: "I thought it would be fine to walk through the park rather than the street - it had been a nice day.

"But when I got to the gate it was locked. There were a lot of people still inside.

"I wasn't worried, but the pregnant woman who was there was. She couldn't just get out by jumping over a fence or something like that."

Marisha's 15-year-old son Abrial Jerram then arrived to help rescue them. Meanwhile she phoned 101, and Camden's out-of-hours parks team for help.

Eventually Abrial found a "secret" gate near Lauderdale House that allowed people to escape at about 10.45pm.

Camden Council said a bell is usually rung 20 minutes before it is locked, and claimed an officer arrived on site half-an-hour after being called - which Marisha disputes, saying no one had arrived by the time the park was cleared 45 minutes on.

She said: "My son went back in afterwards to do a final sweep and found people jumping into Swain's Lane to get out.

"I don't get why you would lock up a park with people in and not check.

"It was clear quite a few people were left in there and it's not safe."

A council spokesperson said: "At this time of year the locking process at Waterlow Park begins at 9.30pm and finishes at 10pm.

"Part of this process involves the ringing of a warning bell throughout the park 20 minutes before it is locked.

"The opening and closing times are clearly displayed on the park signs and we urge all visitors to remember to adhere to these times in order to avoid incidents such as these."