Walking around Covent Garden last Tuesday, I found myself nearly knocked over by a speeding police car with no sirens or lights down a small street. I thought it was strange: such hurry and no warning system.

As I reached Tesco in Covent Garden, I saw six heavily armed police officers surrounding some-one. I walked past and saw a small, middle aged, Indian man. He was holding a white charity bucket in one hand. Two police officers were standing behind him telling him not to move and to spread his legs; they were going to search him. Another two officers were taking all his belongings out of his small beige rucksack and reading every piece of paper and asking him about its contents. At the same time another officer was asking him who he was, what his name was and why he was behaving suspiciously. Someone else was going through his wallet. The man spoke broken English and he did not seem to quite understand what was going on. He kept saying he was collecting money for charity and you could see from his body language and the way he was looking at them that he was stunned and very scared.

These men were tall, heavily built, all Caucasian, talking loudly, moving him around physically, going through his things and saying he had been reported for suspicious behaviour. Someone, they said, had seen him collecting money for charity outside Covent Garden station and had called the police saying they had seen a terrorist. You could feel the adrenalin rising in these men as they went through his bag and I remembered the terrible outcome with Jean Charles de Menezes six years ago.

If a Caucasian man or woman had been standing outside Covent Garden station with a charity bucket and a rucksack would someone have rung the police reporting a 'possible terrorist'? Do people go around calling the police every time they see a Big Issue seller? Or one of those chuggers? They look more threatening half the time than this small framed middle-aged man. But then, Jean Charles had no padded jacket on and did not jump over any tube barriers, as was first alleged. He was not even carrying the dreaded rucksack. But he was the wrong colour. The colour of a terrorist.

They spotted me watching and I felt myself get worked up. I wanted to cause a scene. To let people know what was going on here. I said 'Racists' out loud. They heard me and none of the armed men could look at me in the eye. But an Asian bobby who had turned up couldn’t stop eyeballing me. I stared right back.

After reading all his personal papers, and telling him they thought he could be a terrorist, they had to admit they had found nothing. They formed a ring around him. They could see me watching, so they blocked my view. The biggest of them was laughing and asking where he should go next? 'To the next brown man', I suggested. He ignored me. People walked by but no one could see what was happening because they had ringed him in. It was clear now that he was not carrying a bomb- so now they formed a tighter ring around him- to hide what? The fact that they had been searching a man based on the colour of his skin, perhaps?

After half an hour the armed police officers left. Two plain clothes were left taking his details and the Asian bobby kept eye balling me. I had nothing to hide. I eyeballed him back. Eventually they walked away and the man was left crouching in the street putting his things away. I went up to him and put my hand on his shoulder. Asked him if he was fine. I did not want to scare him. I told him I had seen what had happened. He seemed wary and said yes he was fine. I said I would have been scared, I was scared because of how many men there were. And his eyes started to fill with tears and he said yes he was scared but he was okay. He asked me my name and where I was from. He said he did not understand why he had been stopped. I told him it was because he was carrying a rucksack, he did not understand what that word meant, and because he was brown. He understood that with resignation.

Just as I was asking him if he needed anything the Asian bobby turned up again. They had been sitting in the police car watching me. He looked down at where I was crouched with the man and asked me if I was okay. I said 'yes thank you fine'. He would not move. He looked at my brown paper bag from the teashop in Neal Street. There was a terracotta tea pot in there and some jasmine tea. I told him I did not have a bomb and would he like to arrest me for being brown too. He said nothing. I said I am having a private conversation please would you go away. He said I heard you called us 'racists' and I wanted to explain that we are not and I am Asian as well. Good for you, I said. You stopped this man because of the colour of his skin. He started to say no and get quite pushy. Provocative, I would call it. I was not going to be riled. I told him I was exercising my human right to have a private conversation, he was disturbing this, he had no legal right to stop me from speaking to someone and to go away. He would not go away. He said he wanted to explain to me why they had stopped this man. Perhaps he thought I was from the press. Perhaps he thought this would go further. I turned my back on the bobby and finished my conversation with the man. I wandered dazed and upset into Tesco to get away from the meddling bobby, who would not even let me extend some generosity to the man they had just harassed.

After aimlessly moving through chillier cabinets and food aisles, I went to leave and there he was, resilient, by the entrance, with his white charity bucket. He was not making any noise. Just silently standing there with his bucket collecting for charity. We spoke some more. He seemed stunned but he thanked me for being kind to him.

This incident is a sharp reminder of what the so-called 'war on terror' has done to us. Take this incident and change a few variables. The man had a beard and was wearing Muslim dress. The man was younger, resented being stopped, and resisted the police. The man had no papers to prove who he was. The man didn’t speak any English. The man had a Koran on him and anti-war literature. The man knew people who wanted to teach him a lesson for annoying his neighbours, and who reported on him. All these and you are one step closer, perhaps, to cases like those of Baber Ahmad and Shaker Aamer, who is still languishing in Guantanamo Bay detention camp.

Wrong place, wrong time, and most definitely the wrong colour.