Rob Green: 21 days that changed my life

Without doubt, it was my finest moment in football. In front of a crowd of around 500, I was in Dagoretti, one of Nairobi's many slums, surrounded by burnt out cars, fighting stray dogs, free-roaming chickens and glue-sniffing street children. There was litter strewn everywhere and it was a dust bowl of a pitch but, all modesty aside, I scored one of the greatest goals the beautiful game has ever seen.

Playing for the British consulate against Railway Wanderers, I had already abandoned my traditional role of goalkeeper after refusing to dive in among the glass and rocks to save the opening goal of the match, and roamed the midfield in an attempt to be a bit more of a positive influence. After a few minutes a hopeful punt forward came to me in the centre circle. As I took the ball on my chest and turned, I heard a shout from one of my British team-mates: "Go on, go it alone."

Being in the middle of Kenya and at least 45 yards from goal, I thought better of it and, on the volley, smashed the ball as hard as I could over a back-pedalling keeper, one bounce into the roof of the net. There might be a better goal scored this coming season, but I doubt it.

The crowd went wild, I got mobbed and the African fallacy of Premier League footballers being superhuman grew just a little bit more. I substituted myself immediately so as not to ruin the moment.

Come the end of the game, I was beckoned over by the local crowd to take a look at their "main stand". Glancing over, all I could see was more slums in the distance. Closer inspection revealed the main stand to be a row of tree stumps, lined up parallel to the pitch, with chopped and varnished branches on top to make crude but surprisingly comfortable benches.

"Each game we have, we go around with a hat and collect money for our stadium," I was told in perfect English by a spectator who showed some authority among the crowd. I was shown the hat. It had around 100 Kenyan shillings (about 70p). "This is enough to buy one more tree stump from which we will make our bench, we make them ourselves," he continued. "We have no help from the Government, nothing. They are all – how you say – 'fat cats'. But it is our dream to surround our stadium in seating so the people of Dagoretti can sit and watch their football."

It took a moment for it to sink in. These people have nothing. They live in homes made from mud and faeces. They have no water, very little food, and not much hope for the future. But it meant everything to them to build a football stadium that they could be proud of. And they were proud of it. It was their life.

At this point I realised why I had come to Africa.

This was the first summer in a number of years that I had had more than a few weeks' break. We knew back in November that England would not be competing at Euro 2008 – which is not to presume I would have been in the squad, but obviously I'd be at least an interested spectator – and having no family to think of, and spending the last few years' holidays boring myself on different beaches, I thought it would be the perfect opportunity to explore a part of the world that I thought I might never get the chance to see.

I would be able to experience something different, something that I could learn from, appreciate a whole different level of life. And, most importantly to me, perhaps I could even use the status of a Premier League footballer for some good.

Playing professional football you surround yourself in a bubble. For 11 months of the year you don't have a choice of truly experiencing real life. Having left school and gone straight into football, I have played almost every day of my adult life. As far as lives go, I admit I have a pretty great one. But as far as life experiences go, it has been of fairly limited scope.

In a similar way, life as a footballer is self-focused. It can be easy to take for granted the life that you lead. Focusing on the negatives, not appreciating what you have, things that anyone in the western world could be guilty of. As a footballer you live on challenges, whether they are set by fans, managers, media, the opposition or yourself. This summer I wanted something to challenge the habits, thoughts, and beliefs that I had built into myself after 12 years of full-time football.

So around Christmas last year I approached a number of charities with my thoughts on how I wanted to use my summer break. Amref (the African Medical Research Foundation) came across as positive and active and saw my interest as an opportunity they could make something of: to use football and, in particular, the popularity of the Premier League as a vehicle to spread their Aids, HIV, health and peace messages.

On arriving in Nairobi, I found the dusty, bustling streets were jam-packed with rushing commuters, similar to London, but with fewer suits. But there were some instantly familiar sights: the chaotic roads were full of local buses – mutates – half of which were dedicated to a Premier League team, player or ground. There was the Drogba Bus, the Adebayor Bus and the Gerrard Bus. And it wasn't just the buses. Huge billboards lined the streets: Ronaldo, Joe Cole and Fernando Torresselling anything from mobile phones to saving plans. A pattern was emerging.

The first place we visited was Amrek's clinic in Dagoretti, which was positioned next to a sea of makeshift tents. These were filled with refugees from the civil war earlier this year. We met a group of eight children, aged from six to 16, from two related families who had fled from their homes and farms outside the city. Among them was eight-year-old Peter Mwangi, a cheeky-looking boy, with a permanent grin who had just had a cast removed from his broken arm. The children explained, through an interpreter, the ordeals of their families hiding at night in their maize fields for two weeks, while they watched rioters burn down their home and attack friends and family with clubs and machetes.

It would have been a terrible experience for anyone, let alone children as young as this and Peter had not spoken throughout. We asked what the clinic provided and the children responded with answers such as schooling, food, safety, and health checks. Then Peter sprang into life shouting: "Futa!" (Football in Shen, a mixture of Swahili and English). I asked him his favourite position. "Goalie!" This needed no translation. I had found a new hero.

Wandering back out of the clinic, we walked on to a small dust-covered area where a mixed team were holding a football training session. Amazingly, it was almost identical to a specific training session we use back at West Ham. It's not just football that is universal, it seems. Football training is too.

Behind the fence that protected the dust bowl the movement of refugees from their camp had stopped as people enjoyed the training session. The stark contrast between the organisation and skills on show right next to the chaos of broken and lost lives was difficult to avoid.

A few days later we were able to watch a game of football. A rejuvenated Kenyan team were hosting Zimbabwe in a World Cup qualifier. It was carnage from start to finish. The crowds trying to get in five minutes before kick-off were getting restless and swarming the turnstile in an attempt to catch the start. Their anxiety was met by that of the police, who were quick to brandish clubs and bayonets on rifles to clear the mobs.

Inside the ground it was equally manic, with dancing and singing in the stands before, after and during the match. Early and late Kenyan goals sent the 35,000 crowd into raptures, causing surges and shaking within the terracing. I couldn't – rather than didn't – see much of the match, but the exuberant crowd more than made up for it. It was the first time in a long while that I enjoyed watching a game of football on a day off.

The experiences of Dagoretti proved to be warm-up for the streets of Kibera. A two kilometre square slum and home to a million people, it witnessed some of the harshest violence during Kenya's post-election troubles. The Kenyan government barely acknowledges Kibera as a settlement and it is almost understandable why. The size of the place and the problems are so big that it is impossible to decide where to start. Amref decided to start right in the heart of the slum.

Surrounded by thousands of tiny mud huts, the Amref clinic was the only brick building to be seen. The streams of rubbish and bags of sewage line the streets, causing sanitation to be non-existent. Children who could barely walk, roamed the streets alone, picking through the filth for anything they could find.

For me, this was a culture shock on an almost indescribable scale. It was hard to take everything in. I found it a fight not to be sick from the smell. It was difficult to understand, and even harder not to be overcome, by the enormity of it all. This was an education. It took me some time to realise that at the end of a day the stench in the hotel was me and my sweat from the hours spent in such squalid environments.

Amref's work in Kibera mainly consisted of treating HIV and Aids sufferers from two of the 14 villages that make up the slum. Meeting two single mothers who lived "positively" through Amref was an extraordinary and in many ways uplifting experience.

Mildred Kendi was a young lady who had overcome the stigma, discrimination, and physical difficulties of living with HIV as well as the general problems of living in the slum to become a vibrant, positive person who led groups set up to help others in the same way. It was wonderful to see someone so positive and happy regardless of her situation and surroundings. She didn't have money to pay the rent, she watched her neighbours scrub the communal bath after she had used it and wasn't allowed to use the same washing line as them, but she was genuinely happy.

The next time I struggle to rise from bed for a 10.30am training session at West Ham, I will think of her. In fact, I will think of most of the people of Kibera. Friendly and lively, they were intrigued by the "strange, tall white man" walking around their homes. All so positive and happy living their normal lives in such extreme circumstances.

They knew their football as well. In among the homes people would poke their heads round a corner and shout my name. On turning round I would be greeted by another shout of "West Ham" or "England". Shops in the slums may have been made of wood or mud, but they provided the same services as any western shopping centre. The difference being that these would be named after footballing subjects. Football Sold. The Emirates Library, Lineker's Video Store, even to the Real Madrid Battery Charging Service.

Kibera's pitch made the one in Dagoretti look like Wembley. An open drain ran straight through a patch of ground on which it would be illegal to keep animals in the UK. Here, though, it was a children's playground. In fact, it was the only children's playground for the thousands of kids that lived in the area – and they loved it, playing with anything from a stone to a rolled up sock. It staged numerous impromptu football matches.

The main event during my stay in Kibera was a game named as a "Peace and Reconciliation" match for the 14 villages within the slum. Each was home to a different tribe. Each of the tribes went to war with each other during the post-election violence earlier this year. For the match each tribe would be providing two players to make up two sides, and I was refereeing.

I must admit I didn't grasp the enormity of the situation until after the event, when I was told the disturbing recent history of the tribes. What I did notice at the time was the tension – there was even some snarling between members of the teams – which was a huge contrast to the friendly people I was meeting just a few moments before.

This was perhaps the first time that members from other tribes had come into contact with one another since they were in civil conflict, and I was in charge with a whistle. In fact, the game went by without so much as a murmur, but come the full-time whistle there was not the jubilation or celebration that I had witnessed in previous days.

It left me wondering whether we had actually done good or bad by using football to bring the tribes together, or whether it had just antagonised already fraught relations. But as I thought about it more I felt that, no matter how precarious, football had built bridges between previously fighting groups and I guessed I would have to leave it to Amref to decide on how to develop this.

What I knew for sure was that the sights, sounds and people of Nairobi had given me a life experience that I would remember long after those I had visited had forgotten me. I would not be able to tell you where I went to for my summer holiday last year. This year, I will never forget.