Fragile of mood this week, I had to take my cheer wherever I could find it. As luck would have it, a tin of Fortnum & Mason Chocolossus biscuits left over from Christmas fell into my arms as I attempted a little mood-lifting clear-out of what is known as the treats cupboard. Do you know the Chocolossus? If you don’t, you should. The biscuits themselves are so enormous and dense and livid with chocolate that just one is a serious undertaking, requiring about five minutes to eat, a knife, a napkin and the sort of focus and commitment not normally associated with a teatime snack.

As you begin to eat this ought-to-be-illegal fare, you are aware of drastic changes taking place, not just to your blood sugar and caffeine levels but even to the central nervous system, the auricles and ventricles of the heart, the chambers of the brain. It’s as though you are drinking a triple espresso, a double whisky, and have consumed 10 cigarettes, all while standing on the edge of a very high cliff, looking down at the tiny people scuttling about below and wondering what on earth they think they’re doing. You experience a sharpening of all sensation that is deeply exhilarating; a kind of extreme clarity; a freshly heightened outlook almost livelier than life.

F&M rightly calls the Chocolossus the “definition of satisfaction” and claims it causes “great excitement among true biscuit-lovers” but this is a woeful understatement. I was so stimulated afterwards I jumped out of my seat ready for anything. I half hoped an intruder would present himself so I could administer one or two swift karate chops and be branded a hero. I wondered if it were time to begin and complete that sonnet sequence I have been thinking of writing for two decades now. Alternatively, I might swim the channel - a round trip, why not? - and break the record while I was at it.

So intense was the experience that after this initial burst of energy, which lasted 20 minutes when anything seemed possible or even likely, I sat completely still in my chair for a further 20, stunned and fizzing. I had the strange sense that something unpleasant in me had been cauterised. Then I had to lie down. I slept deeply. These are biscuits so powerful that they actually require a period of convalescence ...

When I woke, I picked up two volumes of travel writing, as my Henry James support group was gathering later that night and I knew I would have to present some intelligible thoughts. English Hours and Italian Hours were the texts that had been set. The trouble with James’s travel writing, it seems to me, is that it isn’t the novels, and you want it to be. You long for complex characters when none exist, for none were intended. It is as though your favourite portrait painter has been told he must only do landscapes.

I read the master’s essay on Venice, slightly losing the will to live: “The churches in Venice are rich in pictures...” As a sentence by a genius, it was awfully low. (“Where was the brilliantly rendered staleness and claustrophobia of the Venice of The Aspern Papers?” I grumbled.) It was with trepidation that I began the London essay, fearing more of the same. For all its faults I love this city as much as I love anything.

“London is positively and in certain ways the spoiled child of the world.” I read on, and gradually a lovely realisation spread about me: the master on Venice was nothing like as good as the master on London. “Well, of course,” I thought.

That London had somehow won this inspiration competition made me feel bizarrely joyous. My city had triumphed. I felt personally responsible, as though I had coached it.

It was an idiotic sort of contest to revel in but needs must and, besides, how could I compare, without grinning, James’s comment on Venetian shops - “You have looked repeatedly at every article in every shop window and found them all rubbish” - with his take on the London variety: “It struck me as desirable and even indispensable that I should purchase most of the articles in most of the shops.”

Well, I know that feeling.

James was not uncritical of this great city, oh no: he refers to its occasional heartlessness, its lack of architectural elevation, its troubled light, its want of manners, even calling London an ogress at one stage, albeit a “human” one.

Yet his conclusion that it is the place “in the world that communicates the greatest sense of life” was music to my ears, better even than music. “I know,” I murmured into the yellow covers of the book, “I know.”

— Financial Times