Slavery continues to blight the lives of many millions around the world. Although officially abolished in some countries two centuries ago, people trafficking, bonded labour and child labour still exist.
Slaves come from the poorest communities in Niger
There are some places on earth that few outsiders visit or know about, vast empty sections of the earth where time has stood still for centuries.
Niger is one of those places. It is a country that you can drive through for hours without seeing a soul.
A nation of vast, barren and windswept landscapes, a country of people who live almost entirely off cattle, and off the labour of human slaves.
Slavery in Niger is not an obscure thing, nor a curious relic of the past, it is an intrinsic part of society today.
A Nigerian study has found that almost 8% of the population are slaves.
You wonder how this can be in the 21st Century and why people do not know about it?
We began a journey to find out more.
We drove for hundreds of miles north across the desert. There were no roads for much of the journey and our cars rattled and jarred across plains set with, what seemed like, solidified waves of sand every few feet.
We choked on the dust, hour after hour, wondering if we would ever see another human being at all in this desolate place, let alone a slave.
We were heading for a well, owned by a local nomadic leader and we had been told he, like many here, owned slaves.
We eventually found his tents and reversed our cars immediately, hoping to locate his slaves without his knowledge first, so that we could speak freely to them, without them being afraid of intimidation.
We found the slaves' tents some way off, and there we met Fatima, a mother of seven children.
She lived in a scrawny brown tent that rose no higher than my elbow off the ground. Her children were all around and one of them had a face bloated with a terrible infection for which she had no medicine.
She seemed humiliated by her status, but seemed to have no greater expectations of her life
Fatima told us she had been working for her master for as long as she could remember.
She said her master did not pay her, but fed and clothed her.
"What can I do?" she said. "I have no money, I need food, I have children and so if I can work for a man who at least feeds me then that is good."
When I asked her if she was a slave she looked at the ground, and said yes.
She seemed humiliated by her status, but seemed to have no greater expectations of her life.
When we spoke to her masters they denied owning slaves. The practice of slavery was outlawed in Niger last year.
Trading in slaves has been banned in Niger since the days of the French colonists in the last century, but ownership of slaves was never specifically banned.
Most slaves in Niger today are the descendents of slaves who were kidnapped in wars and raids centuries ago, and were simply born into their status.
Many slaves in Niger are appallingly abused by their masters.
Slave children are taken away from their parents before they are two-years-old, to break the bonds between parent and child and to eliminate any sense of identity.
The children grow up working in the house of the master.
Assibit was born into slavery, as was her mother and her husband
The slave owners encourage the slaves to reproduce to increase their numbers, sometimes even determining when they have sexual intercourse.
They treat the slaves like their cattle.
Slaves are often beaten for small misdemeanours.
They work long hours and are sometimes deprived of food as punishment.
There are documented cases of slaves being stripped naked in front of their families to humiliate them, of female slaves being raped by their owners, and even of male slaves being castrated by their owners as punishment.
Hopes and fears
Assibit, another slave we met, could not bear the punishment any longer and ran away from her master last July, leaving her husband, also a slave, behind.
She undertook a traumatic journey back to her former owner with us and a human rights worker to see if, under Niger's new laws, her husband could be freed.
When we got to his tents, she lowered herself in the seat so that she would not be seen.
The human rights activist confronted the owner, a lanky thin older man, surrounded by his tall sons.
They became aggressive and began to shout at us to turn off our cameras and leave.
They screamed that the human rights activist was a slave too, and that he deserved a beating.
An entire section of the population would have to be taught that they are not intrinsically inferior to others
We tried to retreat into the car, but our vehicle was stuck in the deep soft sand and would not move.
Eventually, with the sons banging on the windows the car began to plough forward slowly, and we fled.
When Assibit first ran away from her owners she was asked what it was like to be free, but she did not understand the question.
She did not understand the concept of freedom, or even the word.
When I arrived in Niger, I could barely believe that slavery exists in this century on such a scale, but when I left I could not see how it could end in our generation.
Ending slavery in Niger would require a social revolution.
An entire section of the population would have to be taught that they are not intrinsically inferior to others, but that is what they have believed for generations.
The slave owners, and the establishment, are reluctant to teach them.
From Our Own Correspondent was broadcast on Saturday, 12 February, 2005, at 1130 GMT on BBC Radio 4. Please check the programme schedules for World Service transmission times.