The journey into Stone Town, Zanzibar from my holiday hut on the beach took forever. The “bus”, was actually a flatbed lorry, with benches along each side and a roof.

The journey into Stone Town, Zanzibar from my holiday hut on the beach took forever. The “bus”, was actually a flatbed lorry, with benches along each side and a roof. To get to a seat, I had to crawl in past the other passengers. It felt more like a cattle truck. I have to be honest. I was only going into Stone Town because I thought I ought to. I knew that somewhere near the Anglican Cathedral, was the location of the slave market.

Stone Town is a nightmare to find your way around. Narrow streets shut out the sun so you have no sense of direction. Eventually someone showed me the way. The small museum was built around the old slave holding cells. Below sea level, they regularly flooded. In airless, wet rooms, chained to the walls, the hapless Africans waited to be sold and transported. Outside there was a life size sculpture of five slaves chained together - linked by their metal neck collars. My skin went cold despite the heat of the sun.

Yesterday was Freedom Day when we celebrated the bi-centenary of the abolition of the slave trade in Britain. It almost feels as if there is a Wilberforce band-wagon with everyone jumping on it. It can tend to take away the tremendous struggle that those abolitionists went through to effect the change. There is no doubt that what kept them going was the vision of freedom for all. As Evangelical Christians they took God at His word. Inspired by the prophetic books of the Old Testament and the call of Jesus on their lives to “set the captives free”, they battled against powerful economic forces and prejudice that said that the slaves were cattle rather than human beings.

A scene from the film Amazing Grace shows a meeting between the ageing John Newton and Wilberforce. Once a slave trader, Newton was powerfully converted to the Christian faith and convicted of the part he played in this awful trade. He weeps as he recalls that each of the slaves he had shipped had their own beautiful African name. Enslavement had reduced them to numbers: their value no longer inherent because they were made in the image of God and created by Him, but rather in their “fitness for purpose”.

I had always thought that the putative slaves were hunted down and captured. Little did I realise that often it was their families who had sold them into slavery. It is the same today with the women and children who are trafficked across the world to provide sex to a sick society (see, for example www.stopthetraffik.org). Just within the UK, there are over 4,000 women being exploited in this way. Sometimes they have been sold by their families, or else they have been tricked into false offers of jobs in the UK. Their passports are taken away and they then become chattels to be bought and sold. The price varies with their “freshness”. If a woman resists or gets pregnant then her price drops like a stone.

I cannot imagine what it must be like to be sold as a commodity. To be coded and exploited. To have no free will to decide when I get up, where I work, when I go to bed. To not be able to earn my own money, walk freely, or have a social life. To be forced to have sex with whoever has the requisite £25 for each half hour of my working day.

The link is undeniable between the situations then and now. Both entail enslavement for gain; reducing human beings to mere numbers; items for sale. In order to commodify people, you have to take away their freedom. That's how you make the money. All very rational.

It was when I was watching the recent BBC2's programme The Trap that I made another connection. The documentary has reminded me of Aldous Huxley's book Brave New World. Adam Curtis, the presenter, explores how Game Theory has affected modern political thinking. The theory is based on the flawed presumption that a sense of public duty is an illusion and that people are only motivated by self-interest. As an economic theory, it proposes that the best way to order society is not through democracy but via a free market. Instead of relying on altruism, set targets for everything. Control everything by a complex system of audits. Think of people as machines without feelings.

Behind it is the same mindset that created the slave trade and sex trafficking. This is not how we are made. God has created us with a heart made to love, rather than programmed to act “rationally”. Society can only function in a healthy way if we have other people's interests at heart as well as our own. That way lies true freedom for all.