A huge lorry charges down a busy street, ploughing cars out of its way. Pedestrians are mowed down– injuries and casualties everywhere. Petrol leaks and the threat of explosion is imminent as emergency respondents pour on to the scene.

Bedlam – injured bystanders lie prostrate on the pavement – their insides hanging out. There’s blood on the tarmac and wailing children. A mother cannot find her child and someone is wailing hysterically, impossible to calm down in the chaos.

Police try to get the scene under control, trying to calm any survivors and make their way to the culprit, still alive behind the wheel with his head split open. But their job is made difficult by fire crews, ambulance workers and neighbourhood watch volunteers getting in the way. They all need to work together, but no one knows how.

Imagine a terrorist incident like this somewhere like Golders Green high street or Hendon central. In Barnet, 14.8 per cent of residents identify as Jewish –more than in any other local government area in the UK.

“If there were ever to be an anti-Semitic terrorist attack in the UK, chances are incredibly high it would happen in Barnet,” said Barnet MPS’ detective chief superintendent Simon Rose. “Hopefully this would never happen – but we need to make sure we are ready in case it does.”

To prepare for the worst, Hendon’s Met police training campus in Aerodrome Road hosted a training exercise unlike any other on a wet afternoon on Monday, February 27. The aforementioned scene was set up and played out in shockingly vivid detail. Volunteers were made up with fake blood and gore, coached to make as much noise and bedlam for the training police as possible.

Fire brigade and ambulance service staff were on the scene too, carrying out their roles as well as they could – along with community safety volunteers groups Shomrim and the Community Security Trust (CST). While their job was to basically “get in the police’s way”, according to London Fire’s Barnet borough commander Steve Leader, the experience was educational for all.

Mark Gardner from the CST said: “This was a valuable training exercise made sadly necessary by the current situation. You can never really train enough for such potential problems and it helps build relationships which will really be needed if ever we find ourselves in a time of real crisis.”

Mr Gardner refers to the “current situation” – in Barnet, a spate of anti-Semitic crimes and near-miss attacks took place over the course of a single weekend in January. A family’s window was put through with a brick marked with offensive markings, a woman was pelted with eggs in the street and graffiti showed up on billboards and Tube trains with anti-Semitic sentiments. Times are tense for Barnet’s Jewish residents and it’s in times like this the community needs to know the authorities are ready to keep them safe.

It isn’t often these kinds of community reassurances look like a scene from Die Hard, but it gets the message across effectively. While the different teams clearly ended up standing on each other’s toes and almost making things worse for one another, they all learned their shortcomings and how they can use their different functions to plan an effective response to this kind of devastation.

DCSI Rose said: “We need to be ready for this so we aren’t caught short if it ever happens. While I can’t say our performance was perfect today, there will be an extensive debrief to work through what can be improved. This has been a valuable day for everyone and I’m proud of all those involved for their contribution to making our community safer.”