Mystery of Highgate explosions that go bang in the night is solved

Mysterious Highgate explosions solved? local resident Alex Colias found a used flashbang and smoke grenade near the entrance to the tunnel on Parkland Walk. Picture: Nigel Sutton © Nigel Sutton email pictures@nigelsuttonphotography.com

Grenades could be the cause of mystery “explosions” that have baffled residents in Highgate - and they pose a serious threat to a colony of bats roosting in abandoned railway tunnels.

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A used smoke grenade cannister was found near the Highgate Tunnels Bat Project. Picture: Alex Colias A used smoke grenade cannister was found near the Highgate Tunnels Bat Project. Picture: Alex Colias

Alex Colias found a flashbang - a non-lethal grenade - and a smoke grenade canister at the entrance to bat hibernation sites in the Highgate section of the Parkland Walk on Saturday.

The IT security consultant, who moved to Holmesdale Road, Highgate, last month, believes the canisters to be the source of loud bangs that have confounded residents for 18 months.

“I’ve heard the sounds about three or four times since I moved to the area, and it seemed to always come from the same direction,” the 36-year-old said.

“I thought it was going to be kids messing about with firecrackers, but noticing it’s actually in an area where they are trying to do conservation work with animals that are protected, that’s what got me more motivated to get it stopped.”

A 'grenade simulation device' was also found near the tunnels. Picture: Alex Colias A 'grenade simulation device' was also found near the tunnels. Picture: Alex Colias

Mr Colias reported his discovery to the Department of Environment, Food and Rural Affairs, which has referred him to the Bat Conservation Trust.

Bats and their roosts are legally protected and disturbing them is a criminal offence.

The two canisters were pushed through the bars of a locked steel gate, designed to prevent anyone from getting too close to Haringey Council’s Highgate Tunnels Bat Project.

A spokesman from Natural England, a government body responsible for protecting the natural environment, warned that a smoke grenade could suffocate and kill the bats roosting in the disused Highgate railway tunnels.

While smoke grenades do not often cause loud bangs, grenade simulators - often used as a military training device - produce a very loud explosion sound.

When it was set off, the sound could have reverberated through the disused railway tunnels - perhaps explaining why explosion sounds have been heard over a large distance, from Muswell Hill and Crouch End to Shepherd’s Hill in Highgate.

The booming noises are said to be so loud that they cause houses to shake in their foundations and have been likened to a car bomb or gas explosion.

Officers from Haringey Police are to investigate, while Haringey Council staff will visit the site to see if they can find more canisters.

The council also confirmed that those running the bat project do not use smoke grenades or grenade simulators as part of their environmental work.

Mr Colias, a semi-professional photographer, added: “My main concern is for the animals. I’m sure someone’s not doing it maliciously.

“It’s likely they set off the explosion and then the bats fly out and it makes for a cool shot, that’s putting myself in their perspective.”