Typhus and tuberculosis were endemic, while the sight of frantic men and women desperately searching for their children amid both the living and the dead was unutterably painful.
My memories of that time are raw. We saw anger, brokenness and destruction on a scale that is difficult to comprehend today. But there was something else, too.
Many of the survivors had behaved with courage - a courage that enabled them to maintain a dignity while naked and abused, a courage that made them help others stay alive while close to death themselves.
In the circumstances it was an extraordinary testament to the strength of the human spirit. In Belsen and the other camps I visited, I didn't think in terms of human rights; I thought in terms of survival, hanging on to my sanity while trying to make sense of the chaos around me.
The courage of these survivors was an inspiration, an example of mankind's potential for nobility. Three years later the UN's Universal Declaration of Human Rights sought to put that nobility into words.
The declaration, which became a template for human rights legislation worldwide, and the battery of international laws now being brought to bear against former Chilean dictator General Pinochet, was a document born of its time. At the end of the war there was a sense that something had been won, that something rather terrible had been eliminated, and man was somehow liberated.
But the declaration's arrival passed virtually unnoticed. There may have been visionaries who understood that something really fundamental had been achieved, but it didn't have much meaning for the ordinary man and woman in the street longing for an end to rationing and the chance to exchange their utility clothes and furniture for something new.
It took time for its existence to infiltrate into people's consciousness, and when it did, the phrase human rights crept into the vocabulary, and a movement was born.
It's a collection of words that has an almost psalm like quality - the ideals it voices touching every aspect of what most human beings hold most dear. For me it has Biblical force.
Article One just about says it all: "All human beings are born free and equal in dignity and rights. They are endowed with reason and conscience and should act towards one another in a spirit of brotherhood."
Of course, many countries have fallen a long way short of such lofty aspirations, so much so that in 1985, having spent years as a human rights activist listening to the testimony of those who had suffered under the new dictatorships such as Chile and Argentina, I and a group of concerned health professionals opened a centre dedicated to treating those who had suffered torture.
Today the Medical Foundation for the Care of Victims of Torture has helped more than 14,000 torture survivors in the UK. Our clients, from 91 countries, are mostly adult, although sadly we also see children who have either been tortured themselves, or have witnessed acts of extreme violence against members of their families.
Over the years the number of people turning to us for help has grown steadily, with more than 2,200 new clients arriving in 1997 alone. Together with those already receiving our assistance, that figure represents more than 50 people visiting our north London treatment centre each day.
It is Article Five that underpins our work: "No one shall be subjected to torture or to cruel inhuman or degrading treatment or punishment." But it is Article 14 that brings many of them to our door: "Everyone has the right to seek and to enjoy in other countries asylum from persecution."
On arrival here, those from countries like Iraq and Somalia usually sail through the system and their claims for asylum are quickly granted. Others, far too many others, find that they are greeted with disbelief and hostility, and treated as parasites.
It is a view that prevails in the government's proposed new Asylum Bill which intends to deprive refugees of cash benefits and disperse them around the country while their claims are assessed.
Among the Medical Foundation's objections to the bill, we see the "no cash" provision as dehumanising - imagine not being able to pay for public transport, public conveniences or a bag of sweets for the kids - while the dispersal plans will inevitably be to the detriment of many torture survivors who need the specialist care of the Medical Foundation.
The proposed bill is evidence that even in the developed world, governments fall short of the sentiments expressed in the declaration adopted by the UN's General Assembly on December 10, 1948.
But it is only when a government embraces those principles that make real demands that a nation's true commitment to human rights can be measured.
Helen Bamber OBE is founder/director of the Medical Foundation for the Care of Victims of Torture