The unseen teams working to keep Carnival safe

Above ground a million people are enjoying the sunshine, sights and sounds of the Notting Hill Carnival, but in a darkened basement a few streets away around 100 people are working to keep them safe.

Welcome to the ELT - the Event Liaison Team - the people monitoring Carnival's route to try to avoid dangerous overcrowding or other trouble.

On Bank Holiday Monday BBC London was invited in for the first time to see how this operation works.

There's a gentle hum of activity across the room, lots of pointing, lots of looking at maps on the walls.

Crowd control signs at pinch points across Carnival helped to manage the flow of people

There are screens everywhere - teams from the carnival organisers and the Metropolitan Police monitoring incoming feeds from cameras on the route, and from the Met's helicopter flying above.

Reporting in too, are behaviour experts along the route, looking at the mood and density of the crowds.

Each lorry on the parade route has GPS on it so teams here can follow them.

Each sound system is in radio contact with this base and - new this year - crowd control signs at pinch points across Carnival to manage the flow of people and help prevent crushes.

All of this is controlled in real time from a desk in the basement.

There was less serious violence at this year's event, according to the Met Police

Across the room are teams from the London Ambulance Service and London Fire Brigade, the local council, St John Ambulance and British Transport Police, who meet every hour for a catch-up on how things are going.

It's a well rehearsed set-up - but a bigger one than previous years, with more cameras to monitor and more information coming in.

Organisers want more of the same for next year. That will mean making big calls to central government for the money to pay for it.

'Safer event for all'

In updated figures released on Tuesday, the Met Police said 528 arrests were made over the two days of Carnival.

There were 200 arrests on Sunday and 328 on Monday, with 61 arrests following an identification using live facial recognition.

There were two stabbings, but the Met said neither led to serious injury.

Last year, here were 334 arrests during the event, eight people were stabbed, leaving one person dead. Another person was killed in a separate attack.

The force said this year's event saw far fewer" incidents of serious violence than in recent years.

"Delivering Notting Hill takes a real partnership effort. We thank the organisers and others who spoke out in the days and weeks ahead of the event to emphasise what Carnival stands for, to reject violence and to urge anyone planning to come for conflict or confrontation to stay at home," said Deputy Assistant Commissioner Matt Ward.

"I have no doubt their interventions have helped to make this this year's Carnival a safer event for all."