The men, two Sudanese and one Eritrean, held on for over three hours as the coach made the 100-mile trip from a shopping centre in Calais.

Somehow they escaped surveillance cameras in the Channel Tunnel.

They then survived the journey through to Ingatestone, near Chelmsford, ­Essex, wedged into a narrow space ­between the chassis and the ­engine – just inches from the ground.

When the coach stopped the ­dishevelled trio emerged ­covered in dirt and oil and ­staggered off.

But the school caretaker and ­parents gave chase, leading to all three men being arrested and handed over to the UK Border Agency.

Caretaker Keith Britten said: “The first I saw of them was when I was helping to pull out the cases.

“I saw a face and I thought ‘That isn’t one of the parents’.”

A group of 47 pupils and six teachers from Ingatestone and ­Fryerning Junior School had been on a three-day trip, returning at 5pm last Thursday. It is thought the immigrants climbed under the coach when it stopped at the Cite Europe shopping centre in Calais.

Rob Perry, a teacher on the trip, said: “These guys just got lucky and, looking at them, they must have been really desperate.”

Ron Gardner, of Gardner Travel, which owns the coach, said: “I have spoken to the driver and he told me that all of the relevant checks were done in France. I just cannot believe that they didn’t get picked up.”

Last night the UK Border Agency said two of the men – a 28-year-old from Sudan and a 20-year-old from Eritrea – were still in detention.

Source: Express.co.uk