To have a stranger expose himself to you once, is bad luck. But three separate strangers? On three separate occasions? Maggie O'Farrell fights back
There's a pattern emerging. Men keep showing me their penises. Now some might say I shouldn't complain, but I'm talking here about display without good reason. Penis without provocation.

The first time, I was in a phonebox in the middle of a busy street market. I was having a conversation with my friend Sara about where we were meeting that night when there was a sudden and aggressive banging on the glass. I broke off and turned around slowly, displaying my bottom teeth in what, I've been told, is my most menacing face. There was a man outside - smallish, muscular, mid-40s, wearing an inadvisable hat with earflaps. "Oi!" he bawled, "how much longer you going to be?" I stared a bit longer before covering the mouthpiece with one hand and saying very clearly and calmly: "I've only been on the phone for eight-pence-worth, so I might be a bit longer if I feel like it."

"You've been on half an hour," he shouted, quite obviously in the grip of a psychotic episode. "I have not," I countered, cross now, "so piss off, ugly."

In retrospect, maybe I shouldn't have added that last word. Earflap man's response was to unzip his flies and wap out his wanger. There was a pause. I must have looked unimpressed because he waved it about a bit and then pressed it up against the glass. "Are you alright? What's going on?" Sara was twittering down the line. "You won't believe it," I said, "there's a man outside with his penis out." Sara was interested. "Really? Is it erect?"

"No," I told her. "It's squashed against the glass."

I rested the receiver on the top of the phone and shoved open the door with my foot. The man staggered backwards. "That man," I yelled at the busy street, "was pressing his penis against the glass." Several people looked around, confused. I tried again. "That man exposed himself to me!" It worked. People's expressions melded into outrage and disgust. A few started to come over. Earflap man, his flies now done up, hurried away. I returned to the phone. "Sorry about that," I said. "Now where were we?"

About a week later, I was returning home late at night when, 10 metres from my front door, I came upon a bloke performing one of men's least attractive rituals: peeing in a doorway. I was stepping into the road, tutting and muttering to myself, giving him and his ever-increasing puddle a wide berth, when he turned round. "Yar!" he cried, waggling his hips and his member, pale and slug-like in the sulphurous yellow street lamps. "Yar, yar, yar!" he said again. And then he ran off.

A few days later I am on the Underground in the middle of the morning. A man in a capacious jacket comes and sits next to me. I am reading a newspaper, so don't notice him until he says, "Excuse me." I turn, thinking he's about to ask me for directions; I am all ready to be an uncharacteristically helpful Londoner. "Yes?" I say pleasantly. He has a strange look on his face - kind of desperation crossed with bravura. Then I see he's holding one side of his jacket open and that something is pinned to the lining. I peer at what I rapidly discover is a Polaroid of him masturbating. I leap to my feet. "Jesus Christ," I shout. "I'm getting sick of you lot!" and stomp off the train.

It's a very peculiar impulse - wanting to show someone your genitals. Even the vocabulary for this act is strange: "exposed himself". It makes the perpetrators sound so vulnerable and misunderstood and us deliberately callous, not appreciating this very personal gesture. It makes it sound like therapy - and perhaps for some it is.

I decide that this entire scenario is just not on - this quota of unsolicited penises. What's wrong with me? Have I inadvertently tattooed "I'll show you mine if you show me yours" on my forehead? Something must be done. I go to my local police station, where I describe the three incidents lucidly and clearly. Or so I think. The policeman I'm giving my statement to appears to have a an IQ lower than the number of his limbs. "So," he says after I've finished, "a man outside your flat showed you a photo of his penis."

"No, no," I say - and start again. From the beginning.

"Right," he says, at the end of my second statement. "I've got it now. There was a man masturbating in a phonebox outside your flat." I sigh. This is taking longer than I expected. "I'm talking about three separate incidents," I say. "Three?" he says shocked. I look deep into his eyes. Is that the back of his skull I can see? Is any of this going in? Does he not understand the meaning of the word "separate"? Or "three"? "OK," he announces assertively, "there were three men outside a phonebox." It sounds like the beginning of a joke. "Oh, never mind," I say. "Don't worry."

I'm still concerned that there is something about me that is driving men to this. Once is a misfortune, but three times suggests that I have developed undo-your-flies eyes. So I ask around - and uncover a whole can of worms, so to speak. All the women I tell aren't so much shocked as wearily sympathetic. Everyone, it seems, has to put up with a bit of unwanted how's-your-father at some time or other. One friend was once at the top of a Scottish castle rampart in winter. Temperatures were below zero; the wind speed well off Mr Beaufort's scale. She and her friend were clutching each other, barely able to stand, when the only other person on the rampart - a bloke - dropped his trousers. "How did you feel?" I ask. "Well," my friend muses, "there wasn't much to see. It was so cold it had shrivelled away to nothing." Another friend was driving round a car park with her sister, when a man by the ticket machine opened his coat to reveal himself as nature intended. "It was so funny we drove around to have another look," she tells me. "He got all upset and walked off."

"You know what you should say if it happens again," my friend Isobel tells me. "You say: `That's exactly like a penis, only smaller."

Brilliant! I am delighted. It's the best put-down I've ever heard. I incant it to myself while on public transport or when using phones or while walking along streets at night. I swivel my head from left to right, eyes peeled for untrousered males. I am armed now. Ready for whatever people want to show me. So be warned.

Howard Jacobson is away. His column returns on 5 June