What's behind the teenage mass gatherings known as link-ups?

In March, hundreds of teens running down Clapham High Street hit news headlines

"It should be a wake-up call. When young people don't have enough safe or structured places to go to, I believe that sort of energy can and will spill out on to the streets in dangerous ways."

Jason, 17, is talking about what happened in south London in March, when images and videos of hundreds of teenagers running down Clapham High Street made national news headlines.

Four months on, there's still disagreement over exactly what took place during those mass "link-ups", the role of social media and how to prevent future anti-social behaviour, particularly as schools break up for summer.

Jason is part of the Young People's Action Group (YPAG) which advises the mayor's violence reduction unit, external.

He describes the scenes in Clapham as "chaotic, upsetting and unacceptable", but both he and fellow YPAG member Tyra, 17, believe there are lessons to learn about why link-ups happen and how to stop them getting out of control.

"Overall, young people just don't feel like they belong, so they feel the need to engage in this type of behaviour," says Tyra.

Jason and Tyra are concerned that there could be a repeat of the scenes in Clapham over the summer holidays

But what did actually happen in Clapham over those two days in March?

While some news reports at the time referred to a "riot" and around 100 police responded, officers later said there was no looting or widespread criminal damage.

Witnesses described some teenagers lighting fires and setting off fireworks on Clapham Common, while footage on social media showed others running down the road, with some entering shops and a restaurant.

Shopkeepers told BBC London at the time how they had locked their doors, with one describing it as "really scary".

The Met said five people, including four police officers, were assaulted and six teenage girls were arrested, the youngest aged just 13.

Carole Powell, manager for local business improvement district This is Clapham, tells me that while the incident caused concern for businesses and residents, it was also "quite weird".

"It was mostly damage," she explains. "They were knocking things over, pulling stuff off shelves."

She points to how one shopkeeper selling iPads was surprised to find that the teenagers hadn't actually stolen anything.

Powell puts the behaviour down to young people "wanting connection, social media, boredom, lack of resources and an age-old game of kids acting-up".

Carole Powell represents businesses in Clapham affected by the link-ups in March

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