Birkenau was a purpose-built extermination camp which became the final resting place of hundreds of thousands of Jews and others who were deemed enemies of the Third Reich.

At their murderous peak, the Nazis managed to kill 400,000 men, women and children in a matter of months inside Birkenau’s terrifying underground gas chambers.

As night fell on the camp and temperatures dropped below freezing on November 15, students from schools in Highgate and Crouch End trod cautiously through the dark, relying on dim torchlight to navigate the bleak expanse.

Stepping into one of the many wooden huts that line Birkenau’s terrain, the group’s tour guide for the day explained how hundreds of malnourished prisoners would be crammed inside at night, when temperatures could plunge to -25C during the winter.

He said starvation meant some prisoners weighed as little as 25kg, prompting a gasp from 17-year-old Ellie Sherrard.

“My dog weighs more than that,” said the Year 13 student from Channing School, in Highgate Hill.

It was moments of insight such as this which shone a light on crimes so unspeakable, at times they felt beyond comprehension.

That morning, some 200 students had landed in Krakow, Poland, alongside teachers, journalists and a special group of Metropolitan Police officers.

The trip was organised by the Holocaust Educational Trust (HET), a government-funded group which has been arranging visits to Auschwitz concentration camp for school students from across the UK since 1999.

Karen Pollock, the trust’s chief executive, said: “HET’s Lessons From Auschwitz Project is such a vital part of our work because it gives students the chance to understand the dangers and potential effects of prejudice and racism today.”

From Krakow, the HET party headed west to the city of Osweicim, translated as Auschwitz in German, where the Nazis established a concentration camp at a Polish army barracks in 1940.

After stopping off at Osweicim’s only synagogue, the students were taken back into waiting buses to complete the short journey to Auschwitz’s notorious death camps, which have stood as a museum and place of remembrance since 1947.

Passing through the iron gates to Auschwitz I, one of three camps open to the public, you are greeted with the infamous motto, “arbeit mach frei” (work makes [you] free), a sickening irony.

Inside the camp’s clean bricked buildings are shocking reminders of the horrors that took place some 70 years ago.

Behind glass panes sit tons of human hair, suitcases bearing the names and addresses of their owners and mountains of shoes.

All these things belonged to Auschwitz’s former inmates – a chilling reminder of humanity’s darkest chapter, frozen in time.

The second half of the visit took students up the notorious railway line, immortalised in film, leading to Birkenau death camp, also known as Auschwitz II.

Following a harrowing tour of the camp, which includes the remains of two gas chambers blown up by the Nazis in a bid to cover their murderous tracks, the various HET groups assembled for a haunting candle-lighting ceremony to conclude the visit.

Reflecting on the trip, Rebecca Spens, 17, another Channing student, said: “When you read about the Holocaust, you get quite a lot of shocking figures which are very hard to get your head around.

“Things I saw on the trip to Auschwitz really brought the figures to life in a vivid and scary way. More people should have that experience.”

As part of the HET experience, all students who attended the trip will meet for a follow-up seminar to reflect on the visit with HET educators on Monday.

This follows a seminar held before the trip during which students heard testimony from Holocaust survivor Ziggy Shipper.

For more information about the work of the HET, go to www.het.org.uk