I think my father is dead," the teenager said. "I don't know what happened to him. People said the Taliban killed him but I don't know. I don't know where he is."

Nabi, an 18-year-old from Afghanistan, was sitting in the dust of a transit camp in the tiny Greek town of Idomeni, recounting the horrific events that had forced him to flee his homeland.

He had no idea that the man listening to his story, dressed plainly in black trousers, white shirt and a flat cap, was Chief Rabbi Ephraim Mirvis.

Rabbi Mirvis, together with four other United Synagogue rabbis, was making a secret visit to the camp, next to the Macedonian border, where 10,000 refugees pass through every day.

Rabbi Mirvis asked Nabi two simple questions: "How do you feel? Where are you going?"

One boy made the perilous boat journey. ‘I saw people drown,’ he said quietly

He listened intently as the teenager described how he had travelled alone for 20 days, with no idea where he was heading, finally making the perilous journey across the Aegean Sea from Turkey.

"I saw people drown and no one could save them," he said quietly.

Behind Nabi a line of people stretched away - hundreds of refugees about to embark on the next leg of the journey that they hope will lead them to safety in Europe.

They had been told to sit until their turn came to cross the border through the small gap in the fence that separates Greece from Macedonia.

Nabi's eyes lit up as he told Rabbi Mirvis about his dreams of furthering his education. He said: "I love to study very much. In Afghanistan the security is not good, I can't study there."

The conversation was cut short as Nabi's group was given the order to stand and move on.

"I think you are amazing, good luck," Rabbi Mirvis said, reaching out to shake the teenager's hand.

Nabi waved goodbye as he and 50 other refugees walked through the checkpoint. Within seconds another group took their place.

"A closely guarded secret"

Details of Rabbi Mirvis's visit to the camp had been a closely guarded secret as the plans to send him and four United Synagogue rabbis to the camp, to view the aid work being funded by the charity World Jewish Relief, were drawn up during the past fortnight.

The delegation arrived last Thursday morning, making the 90-minute journey from the city of Salonika by minibus.

The camp - four huge holding tents set in an area the size of three football pitches - had only been there for a few weeks. It was established in September to process the stream of refugees from Syria, Libya, Afghanistan, Eritrea, Pakistan.

World Jewish Relief's Richard Verber explained: "Before the camp was set up here it was just chaos. Refugees were arriving in their thousands to what is essentially just a field.

"There would have been a few people volunteering and handing out food, but that was it. The refugees arrived and just waited to cross the border, but there was no structure, no help and many of them need medical attention."

The Chief Rabbi and his party had been told it was wise to "dress down" in the camp. In the bus they put on baseball caps to hide their kippot. Some donned sports tops while they were briefed on security.

WJR project manager Josh Simons had visited the camp a week earlier to find out how the refugees might respond to Jewish visitors.

He said: "Some people were like 'whatever' but others were more uncomfortable. Perhaps they only understood Jews to be one thing because they come from countries who are not particularly friendly to us, or perhaps it is tied into Israel.

"My suggestion to the rabbis is to get to know them first, judge on the conversations you are having, and if you feel you want to reveal your identity, then do."

The Greek police had been briefed about the visit. Officers gathered at the camp's entrance as the rabbis arrived. After a brief conversation it was agreed the police would keep a discreet distance as they followed Rabbi Mirvis around the camp.

Accompanied by a guide supplied by Praksis, WJR's partner on the ground, he began a tour of the tents, where women huddled in corners, babies cried, and exhausted young children slept on their mothers' laps.

He was invited to sit down by one family who had fled from Afghanistan. They told him: "We had to leave. All of us. This is all we have."

The mother, who looked no older than 18, changed her baby's nappy while Rabbi Mirvis and her husband talked in hushed tones alongside them.

The Chief said he was moved by the stories he heard. "Whether these are refugees from Afghanistan or Syria or Libya, they are all talking about the dangerous lives that they've been leading and the danger their families are in.

"Yet there is a real hope for a new life and desire to carve out a happy existence for themselves. We are just at one single point in their journey."

His fellow rabbi Danny Bergson, of Pinner United Synagogue, said he was overwhelmed by the experience.

"No amount of briefing could prepare me for the experience of seeing people at their most vulnerable," he said. "To hear people's deepest fears and uncertainties was overwhelming. I was moved by their sheer strength and optimism."

"This is a modern-day crisis...technology can help them stay alive"

Rabbi Mirvis noticed that many of the younger refugees were using smartphones, updating Facebook to let family know they were safe.

His guide, Marie Halaka, explained: "It may look to some as a sign of money, but a mobile phone could be as important as food. This is a modern-day crisis - we all have technology and it is the technology that helps them on their journey, it often keeps them alive."

Also accompanying the Chief Rabbi was Rabbi David Mason, of Muswell Hill United Synagogue. He said: "I spoke to two refugees called Shahab and Mohamed. Shahab was Iranian and had met Mohamed who fled Afghanistan in a refugee camp in Turkey. They were broken emotionally. Shahab was shaking as he described the journey across the sea."

Rabbi Mason was surprised that refugees had little idea of where they were going to in Europe. He said: "One family were all together and their parents were already in Germany - they had an address and everything. You could see psychologically there was a clear direction ahead for them.

"But someone else actually said to us, 'where do you think I should go?' I just can't get my head around that."

Rabbi Mason said he "found hope" in the fact he was able to "connect to refugees from countries known for their hostility to Jews".

He said: "You know it was quite amazing, there we all were talking, sharing hopes and dreams and fears, a Jew, Iranian and Afghani. We even talked to a Palestinian volunteer. It actually gives me hope in humanity."

A crowd had gathered as a volunteer entertainment group called Clowns without Borders put on a show.

Ms Halaka said: "It might look strange but this performance might be the first time the children have laughed in weeks."

Dayan Ivan Binstock, also part of the delegation, said he was amazed by the "dedication of the people who come to volunteer and the efficiency of the camp".

For Rabbi Boruch Boudilovsky, from Borehamwood and Elstree United Synagogue, getting a chance to speak to refugees made a deep impression.

He said: "Seeing a three-year-old girl being treated by a doctor paid for by WJR made me proud of our community."

Thanks to WJR funding, Praksis is able to provide food and medical attention to all the refugees arriving in Idomeni. British Jews have donated more than £700,000 to WJR's refugee appeal.

A makeshift courtyard beyond the tents was home to temporary toilets, showers and a "grooming shelter" where men could shave. Teenage boys wearing Gucci belts and Nike trainers crowded in front of the mirrors to tend to their hair.

Ali, 18, caught the eye of Rabbi Mirvis who went over to talk to him.

"Take my photo," the teenager insisted as he combed his jet black hair into an Elvis-style quiff.

The Chief Rabbi asked: "Where are you travelling to?"

All smiles as a family is greeted by WJR project manager Josh Simons

"I don't know," Ali replied. "I just want to be safe in whatever country will take me. Maybe London?"

"Too expensive," another young man beside him called out. They all laughed.

Ali's number was called and he made his way over to the departure tent.

As one group left another was ushered into its place, like a human conveyer belt.

"There is nothing quite like being here"

Rabbi Mirvis said he could not help but draw comparisons to "what, as Jewish people, we have seen before".

He said: "I've been thinking about our past, our Jewish past and journey, and thinking about our sadness. Here being taken into a tent where people are resting I've been thinking about bunkers in Auschwitz where there was a very different end.

"Thankfully these people will have a happy end waiting for them. It will be of promise and of hope."

He added: "Standing here alongside these refugees I'm enormously proud of the British Jewish community and the fact we want to give.

"We are not asking questions, what is important is that they are humans just like we are, they have babies just like we do and I'm proud of the way we have reached out to them.

"Speaking to refugees has made me see the trauma people face could be eased if Europe would sufficiently invest in the hundreds of thousands who are in need."

Rabbi Mirvis said he had wanted to take the delegation from the United Synagogue to see the work the Anglo-Jewish community had already helped to fund, and show refugees that the community "is serious about responding to the crisis in a big way".

He added: "The entire purpose of this trip is the follow-up. Together we will share our experiences and reflections with the community when we get back.

"I want to encourage the United Synagogue and the entire community to engage in a range of initiatives to help refugees. We should not allow this plight to fall off the radar. It is an ongoing crisis and will need an ongoing response."

As the rabbis prepared to leave, they passed hundreds of Syrians, newly arrived off the bus from Athens.

Rabbi Mirvis spotted a mother carrying a small child on her hip, while another older girl held onto her hand.

"Good luck," he told the mother, as the exhausted family were handed bottles of water and sandwiches, and ushered into the camp.

Rabbi Mirvis watched them go. "There is nothing quite like being here," he said. "Until you see it with your own eyes, you can't grasp the work that is being done."