Game of Thrones actress Oona Chaplin was joined by the Bishop of Barking at a service urging David Cameron to act on the “humanitarian crisis”.

The group of campaigners told the prime minister that he should visit the “Calais jungle” and speak to refugees. Yesterday’s service was held at the same time as the start of a court hearing which is set to determine the fate of four children living in the “jungle” refugee camp who have family in Britain.

About 50 people, including Green Party leader Natalie Bennett, met at St Andrew’s Church, Holborn, to remember an Afghan teenager who died while crossing between Dunkirk and Britain.

The youth, said to be called Masud, was thought to have been trying to get to his sister in the UK.

Speaking at the service the Bishop of Barking, the Rev Peter Hill, said: “We ask our government, our prime minister and especially our home secretary: how many more children must die in this way, when they have that clear legal as well as a moral right to be re-united with their families here in Britain?”

Campaign group Citizens UK, which is supporting the children’s asylum case, is hopeful it can pave the way for more vulnerable young people to be brought to safety in Britain.

The hearing to determine the fate of the four children continues tomorrow (Wednesday).