I know people who swear by the charms of Lagos or Grozny. For them, as me, a city is where friends are. Take note, Jan Morris

I once sat next to a woman at dinner who asked me where I lived. When I replied, London, she frowned and said, how simply ghastly for me. "It is an awful place, absolute hell. I hate going there, the people, the traffic, the tube, the dirt. You must be dying to escape."

Stung by hearing my beloved home so abused I asked where she lived. Gloucestershire, she replied. "How ghastly," I said, "it is an awful place, absolute hell. I hate going there, the people, the horses, the filthy lanes, the boredom. You must be dying to escape." How extraordinarily rude, she said, and turned away for the rest of the evening.

Hating cities is apparently fine, but hating the country is not permitted. Now I read that my old friend, the travel writer Jan Morris, has fallen out of love with London. She proclaimed so in last Saturday's Guardian: "When once it welcomed me like a dowager to her run-down stately home, now its greeting is more like the air-kiss of a tabloid celebrity." When Jan steps off the train at Euston, she said: "I find myself entering a different city altogether from the one that used to thrill me."

I take comfort only in the knowledge that disagreeing with Jan is always exhilarating. We have disagreed everywhere, on the slopes of Snowdon, surrounded at Pen-y-Gwryd by mementos of the 1953 conquest of Everest (in which Jan took part). We have disagreed among the Italianate splendours of Portmeirion. We have disagreed on the banks of the swirling Dyfi and in Jan's stone eyrie upstream from Lloyd George's grave in Llanystumdwy. Disagreeing with her is more enjoyable than agreeing with anyone else. She has mastered the art of dissent, which is to clothe courtesy in laughter.

When Jan shuts her computer, packs her bags and waves goodbye to north Wales, we know she is off to discover, or more often rediscover, some exotic clime and dust it with literary gold. She once claimed that her "final book" was Trieste and the Meaning of Nowhere. It was her Tempest, plunged into the Adriatic deeper than did ever plummet sound, and full of life-expiring metaphor. But that was in 2001 and, like Rubinstein, Jan's last appearances are now annual events. The latest, out this week, is Contact!, a book of word sketches.

Great travel writers never just describe places. They report their responses to places and their inhabitants. Some cheat and take along a companion as the butt of their commentary. Laurens van der Post took the hapless cameraman Spode to the Kalahari. Peter Fleming travelled Tartary with the tiresome Kini (who later took her revenge in a Royal Geographical Society lecture). Eric Newby ribbed poor Carless up and down the Hindu Kush, and was equally merciless with his wife on the Ganges.

Jan resorts to no such devices. She does not bring human props to feed her narrative. She lives off the land, knowing that for a city to come alive, she must do more than just see. She must form relationships with local humans, perform some ritual of empathy. Her landscapes are peopled, like Constable's, with dappled ghostly figures to draw the composition into focus.

So powerful are these sketches that, to me, they are more than walk-on extras. They are not of celebrities or interviewees, but of passers-by, faces in a crowd, the chance encounters that furnish the room of the solitary traveller. Jan bumps into a man in a hotel door. When he asks where she is from, and she replies "Wales", he cries: "Wales! How wonderful." Oh you splendid liar, she says, you have never heard of the place, and they both roar with laughter.

Jan winks at a wrinkled Alexandrian cabby, chides an American matron, teases a Polish taxi driver that his Volvo is "not Chopin". She helps a "hard-mouthed, fast-shoving" blind lady across a Paris street and into a shop, after which the lady remarks: "Now I give you back your liberty." These flashes of ersatz intimacy colour the monochrome of travel. They bring Jan "close to the meaning of a place".

But they are more than that. They are the city. My early experiences of visiting America coincided with a youthful eagerness for adventure that made every city beautiful, however ugly. Visiting Germany coincided with so many pleasant meetings as to endear me to German cities ever since, just as unfavourable ones coloured my view of France.

I know people who swear by the glories of Lagos, Kiev, Shanghai and even Grozny. I recall the mayor of Houston in Texas looking out of his skyscraper office and sighing that I surely had never seen a city as beautiful as his. I choked, until I realised that my ugly sprawl of office blocks and parking lots were his glittering array of acquaintances. For him, as for me, a city is where the friends are. The beauty of friendship surpassed the physical attributes of a place, much as the mind surpasses the beauty of the body.

Jan's falling out of love with London has, I suggest, little to do with London and more to do with Jan and her Londoners. The wartime metropolis of her memory was battle-scarred but indomitable. "I truly loved it then," she writes, "the proud battered style of it, the blackened and ruined monuments, the posh-and-cockney mixture, the Union Jack flying gamely through the smog upon the Palace of Westminster, the grimy tugs churning up the Thames – liquid 'istory."

That London had the excitement and anticipation of youth, just as it must now convey the tiresome aggression that irks old age. Jan's accounts of India, Oxford, Venice and a myriad other cities are far more than the application of a cultured mind to bricks and mortar, walls, roofs, trees and water. Each was seen at a different stage in a career and with different human encounters, and therefore struck different chords.

London tries to reject my affection. It disfigures itself with ugliness – now with idiot towers as its mayor, Boris Johnson, vies with Ken Livingstone in their penis envy of New York. It afflicts the visitor with what Jan experiences as she steps from the Euston train, or Gloucestershire deplores as she fights her way across town to Harrods. It afflicts them because they are visitors.

My London is one that Jan and Gloucestershire can never love. I do not spend my time in the city, as most non-residents do, enveloped in crowds, shopping and fighting public transport (which is not that bad). I see a city of local streets enlivened by corner shops, bustling pubs, children going to school, parks, squares, museums, theatres. It is a place of intense calm, if I want it.

More than that, I love the comforting familiarity of a life lived in one place, of the continuity of things and friends, spiced only sometimes by a dollop of change. The passing Jan can play her game of smiling and winking and joshing to score a response. But it is she who is air-kissing London, not the other way round. A true city is a mirror, in which the blemishes are our own.