A group of engineering students got the project of their lives when police asked them to help out with a petrol bomb carrier.

The £50 million police training centre in Mark Lane, Gravesend, is where officers from the Met go for firearms and public-order courses.

The centre makes petrol bombs on site for riot-training exercises, which are held three times a week, and officers need to transport them to the training ground.

However, the old van they used was condemned by a health and safety inspector so the police drafted in the help of some enterprising pupils.

Kevin Nutter, inspector of special crime operations and chief instructor for public order at the centre, said: “We asked Leigh University Technical College pupils to come in and have a look, and work out what sort of trolley arrangement they could mock up for us.

"They gave us a few options, we picked one and in six months they designed it, priced it up and built it.”

It needed to be able to carry 200 bombs at a time, and it was pupils Harry Tindall, 17, Harry Martin, 18, Matthew Moon, 18, Ryan Battledore, 17, and Harry Dressel who came up with the solution.

Ryan said: “This has been quite challenging and really technical, especially the designing stage, but we’ve had a lot of support.

“It’s been great working with the police. We came here for a day and watched a full-scale mock-up of a petrol bomb riot, to show us where the weaknesses were. That was pretty exciting.”

The Mark Lane centre occupies 93 acres and was opened in 2003.

As well as firearms and riot scenarios, around 10,000 officers a year are also trained in ‘rapid entry’ – forcing their way into buildings for scenarios such as sieges and drugs raids – and how to deal with protestors.