I decided on a new strategy, after I was groped by two groovy young South Americans and then commented on lewdly by two Englishmen in their 50s - see, it's just like a Benetton ad - on the same day. Later, I was perusing the peppers in Sainsbury's when someone hissed "Hello, sweetie" into my ear. I turned to see a thirtysomething Middle Eastern guy with clear features and bright brown eyes, wearing a neat shirt and pressed chinos. He must have popped out of the office to bug a woman and pick up some snacks.

"Why do you think it's OK to harass women?" I said calmly, loudly. The man froze, then a look of fear washed over his features. He shrank like a worm. "What?" he snivelled, his eyes sliding to the floor. "I didn't say anything bad ..."

"It doesn't matter what you said, I didn't say that you could speak to me. It's not OK to whisper in a woman's ear when she's going about her business. "

He didn't walk away so much as dissolve, and I marvelled at my new method. How could a compulsive irritant's bravado be deflated so easily? Do they rely on their victims mutely accepting it?

Of course there are degrees of seriousness. On Sunday I was jogging in Hyde Park when two boys of 18 or so rode up on bikes alongside the jogger in front of me. One of them reached out and squeezed the woman's bottom before making away slowly with his friend. She went rigid with shock, and stopped running. I saw the strength drain down her into the ground as she began to shake.

I asked her if she was all right, and suggested that we run together, since the boys had come back into view and were blocking their bikes around two other women who were walking along a parallel path.

We did so, but there was no way to avoid these boys and no way I was going to let them get away with groping three women in two minutes. As we approached I told them I'd witnessed everything, I was going to call the police, how dare they. The boys were well-spoken, and the perpetrator wasn't afraid. He whipped his mobile out of his pocket and tried to give it to me.

"I'm not calling the police on your phone because they'll think that we know each other and that it's all a big joke," I said coolly. "The police are back there, I just passed them. The longer you stick around the easier it is for me to give them a description. There are CCTV cameras all over the park. Can't you see them? You should leave now."

It went on; he was enjoying himself at first. He knew that men who assault women get away with it. We four joggers were walking slowly in a line, like an army, and I shouted righteous things as the boys finally edged their bikes away. As we parted the women jokily congratulated me, their she-knight in sports shorts.

I went on ahead and then, as in a nightmare, I saw the boys again up ahead, watching me languidly. My muscles filled with adrenaline and, fuelled by decades of rage, I began to pursue the boys like a killer cyborg - or a killer midget cyborg in bottle-end specs. They freaked on instinct and pedalled hard but there I was, powering across the park and shaking my fist, miraculously keeping up.

It's comical: two cycling harassers fleeing from a bionic art critic. They were scared by the colossal, muscular force of my anger; but what was I going to do, stand on one chap while I biffed the other? And once the amusement at my own ridiculousness abated, the grief returned. The street harassment, the job harassment, the jokes, the exploitation, are all part of the same thing. Thousands of years into "civilisation" and a woman can't even jog in peace. It's a shame, because endurance sports are the only thing I'm above average at.

· Bidisha is a novelist and arts critic

contactbidisha@hotmail.com