One bright, dusty, midsummer-quiet afternoon last week the doorbell rang and I looked out of the window (to avoid making the long descent from study to street only to find a kid with a box of J Cloths for sale or some pair of credulous bozos with good news about the Lord) and saw that it was the postman.

Well, not exactly the postman. What I had seen was a Parcelforce van, which is better still. Now that Parcelforce is the large-object wing of the Post Office, the Parcelforce guy is more exciting than Postie himself, since Postie is now protected by safety-in-the-workplace guidelines from carrying anything that I might eat, drink, read or hang on the wall.

So I bustled to the door full of the joy of the day, ready to hail the fellow with my breeziest “good afternoon” and take delivery of whatever jolliness he had in his bag. But as I opened it, my hair and whiskers were fair blown back by loud music, a thumping beat and the shouted words: “I’m gonna **** you, bitch! Yeah, bitch! Yeah bitch! I’m gonna **** you, bitch! Yeah, bitch! Yeah, bitch!”

I was more than a little startled. The postman in question, however, a wiry, sullen-looking fellow, maybe 25 years old, with a Parcelforce beanie pulled low on his brow, seemed blissfully unbothered as he wordlessly handed me an electronic thing to sign. And indeed, when I looked out past him towards the noise, I saw that it emanated from his own vehicle, the aforementioned little red van, as little and red as Postman Pat’s, which was double-parked outside my house, in my quiet suburban street, with the windows open and this loud, aggressive rap booming from it: “I’m gonna **** you, bitch! Yeah, bitch! Yeah bitch!”

As he held the electronic thing in my face, the postman (and I insist on calling him a postman, despite his no doubt being officially known at Parcelforce as a “delivery solutions operative”, or some such, because he was delivering my post and was in the pay of Royal Mail Group Ltd) was actually nodding his head to this vile music.

When I was a kid, our postman, Derek, used to whistle as he came down the path with our letters. He may have been whistling a tune whose original words were, “I’m gonna **** you, bitch!” but I doubt it. It was usually Colonel Bogey.

I honestly didn’t know where to look. My house is 50 yards from a primary school. I might have been a little old lady (more than likely if you’re looking for a front door to be answered at three in the afternoon) or a mother with children. How can it possibly be acceptable for a man from the Royal Mail, the Royal bloody Mail, going about what is in theory Her Majesty’s business, to be declaring as he rings your mother’s doorbell, my mother’s doorbell, anybody’s mother’s doorbell, on a quiet June afternoon: “I’m gonna **** you, bitch! Yeah, bitch! Yeah bitch!”?

The man can listen to that kind of sick, sexist drivel in his own time, if he wants. And I dare say that the manager of whatever rap band it was he was listening to will have some excuse up his sleeve about how the song only reflects the sexist and aggressive mores of the street, without specifically endorsing them, but, I swear, if he showed up round my place with that kind of specious bilge I would specifically endorse his face for him.

I grasp that people under 25, people born into the iPod age, cannot conceive of music as anything but a constant backdrop. Music is no longer a thing to be enjoyed for its own sake, at gigs and festivals and in pubs and clubs and at home on a stereo, but is a vain and impotent declaration of self to be blared from cars and phones and laptops and headsets at all times — a constant somatic comfort to the dull, blunt, flabby modern brain. But to crawl the streets of the city playing offensive rap music on full volume with the windows wound down is the sort of carry-on you expect from teenage hoodlums, stabby little respec’-seekers and bug-eyed gang-rapists on crack. Not an employee of the Royal Mail. Not your bloody postman.

I didn’t know what to say to the man. So I didn’t say anything. Maybe if I had he would have shanked me for dissing his tunes. I don’t know, maybe that’s what they teach postmen to do these days.

Maybe, with all these threats to its business from e-mail and private sector courier companies, the Post Office is planning to go a different way to modernise. Maybe it is going to train postmen to carry blades, slouch down the street with their trousers round their knees, pouting and scowling and playing rape anthems on their phones, and asking people what they are staring at, so that they can stab them to death.

Or, I don’t know, maybe, “I’m gonna **** you, bitch! Yeah bitch! Yeah bitch!” is the message the Royal Mail is really trying to send us.

The tune, and its bone-headed, soul-sickening lyrics, stayed with me all day. Try how I might, I simply could not dislodge it from my brain, even with a constant, quiet, wistful repetition of “Postman Pat, Postman Pat, Postman Pat and his black and white cat . . .”

• Every time I do a television show, it’s the same: regardless of its success or failure, regardless of the nice things people write and say, I go hunting for the negative stuff, and dwell on it. And this week has been no different.

The second series of my food history show with Sue Perkins, The Supersizers Eat . . . , began on BBC Two last Monday and did well: good viewing figures, red-top raves, five stars in Heat magazine and another series commissioned. These are the standards by which the television industry — I gather — judges itself.

But the critics in The Guardian and Independent (whose constructive influence is negligible, but which sort of hold more sway with me, effete, liberal, overeducated ponce that I am) found lots of mean things to say. As ever, with those two publications, they were mostly unpleasant personal things about me.

So I ranted and raved for a while about the men who wrote these things. “Why do these miserable ink-widdlers think anybody gives a toss what they think?” I yodelled to anyone who would listen. “Why do critics think it’s so smart being mean?”

Then on Thursday night I headed to Regent’s Park for the Taste of London restaurant festival, to hang out with chefs, eat great food and get rat-arsed. I was chatting to an old foodie pal as darkness began to fall when a slim, dark-haired man introduced himself as somebody or other, “chef at l’Ambassade”.

“What ho,” I said, reaching for his hand, wondering why he looked so unhappy. And then I remembered. Ambassade de l’Ile. I reviewed it only a few months ago. I called the food “dull” and “underwhelming”. I said it was “a Fulham shag parlour” and that my third course was “a blueish confection that looked like Polyfilla and tasted like the secretions of a hyena’s bile duct”.

I stood chatting for a minute, pretending everything was fine, wishing a tree would fall on me (or, better still, on him) and then scuttled off home feeling absolutely sick with myself and wondering, for very different reasons, why critics think it’s so smart being mean.

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