My Venice that day was a city full of tremulous anticipation. I wished to spend the day with Mrs Cort even more than I wished to travel in a gondola around the canals. We met by a landing stage not far from the Rialto, where gondola, gondolier, and a hamper of food already awaited. It was eight in the morning, and brilliantly clear. Warm already, with the promise of more to come. The city itself was sparkling and Mrs Cort – I hope I do not give away too much if at this point I begin to call her Louise – was standing waiting for me, and smiled as I approached, a smile of such warmth and promise that my heart skipped a beat.

Gondolas are not a place for any sort of intimate conversation, although we sat side by side rather than opposite each other. The boats are arranged (for those who do not know) with the gondolier standing at the back, so he had a clear view, not only of the waters ahead, but also of his passengers. They miss nothing, and a flimsy construction over our heads provided only limited privacy. A brushing of hand against hand; the faint pressure of bodies touching in the cramped confines of the hull. It was almost unbearable and I could sense she was under a similar pressure. I could feel the tension within her, longing for some outlet.

And so the morning passed in delicious frustration, the conversation edging towards intimacy, then pulling back before moving closer once more.

'How long have you lived in Venice?' I asked, this being an example of a conversation that proceeded in fits and starts, punctuated by long silences as we were both calmed by the soft splashing of the water against the side of the boat.

'About five months,' she replied.

'You met Mr Cort in England?'

'Yes. In London. Where I was working. As a governess.'

She said this with a slight defiance, as if to see whether my attitude to her would change as a result of learning of her situation.

'How did you come to that position?'

'My father died when I was young, leaving my mother to look after us, two boys and two girls. I was the eldest. When I was fourteen my mother fell ill. So I had to work. Eventually, I was engaged by a family in Chelsea, not rich by many standards, but well enough off to afford me. I cared for their two children until I left to marry. They were delightful children. I miss them still.'

'True love?'

'No. He desired a wife to look after him and I craved the certainty of marriage. It was an arrangement suitable to us both.'

She sighed and broke off to look over the lagoon towards the Lido which was slowly coming closer. I did not wish to intrude, so asked no further, but I understood all too well that she lived in a loveless marriage, deprived of that affection that all human beings must have. It is the situation of many, perhaps it is the normal circumstance of most, and she did not complain of a contract freely entered into. But it is not in our nature to remember how much worse things might have been; we only dream of the better that slips through our fingers.

'And he brought you here.'

'Yes. But I find this dreary conversation for such a day. Tell me about yourself instead. You must have had a more interesting life than I have so far enjoyed.'

'I doubt that. What can I say?'

'Are you married?'

'Yes.'

'Happily?'

Which is the moment I stepped closer to the edge. Yes, happily. My adored wife. I miss her so much. Words acting like an impregnable fortress, able to keep her out, me inside, both separated for ever. I said nothing, and she understood my meaning.

'But your wife is not here. Why is that?'

'She does not like to travel.'

'Does she have a name?'

She was probing, teasing me. Betrayal mounted on betrayal as I turned aside and did not answer once more, then turned back and met her eyes as they looked calmly straight into mine, communicating endlessly, whole volumes about us both.

'And what do you do?'

'I spend my time investing money for gain. It takes up much of my life.'

She looked curious. 'I understand nothing about money,' she said.

'This is not the time to start learning,' I said. 'I find it fascinating and can discuss it for hours, but I also think there must be other topics to talk about when one is in a gondola on a fine morning in the company of a beautiful woman.'

She smiled faintly and looked away. I wondered how long it had been since anyone had spoken thus to her, if anyone ever had.

'I like that,' she said softly.

There then followed the longest silence of the day; our closeness had already grown too great to require words. Instead we both sat quietly, watching the flat strip of land growing closer, I so aware of her it was almost painful.

The Lido has changed greatly since then; now the hotels I once imagined in my mind's eye have sprung up along its length. Then it was all but deserted; the main road was little more than a track that led out of the tiny settlement on the city side of the strip; within a few hundred yards all habitation ceased, and there were instead only cows and a few sheep occupying an island near fifteen miles long and a mile wide.

At the time I was somewhat disappointed; I had anticipated a voyage in the inner lagoon, seeing the sights I thought every visitor should see – Murano, Torcello and all of those. I had not yet seen much even of the main city, let alone its outlying regions, so coming to a place which was virtually deserted, and which had no features of note was not what I desired at all.

'Why have you brought me here?' I asked, somewhat petulantly.

'Wait and see,' she said. 'I love this place. It is the only place where you can be alone. Come.'

She directed the gondolier to pick up the hamper of food and carry it over the island to the other side. She later told me she had discovered this spot many weeks before, and had kept it secret from everyone, treasuring it as a place she alone in the world knew about. To show it to me was the greatest compliment.

The other side was not far; although a mile or more wide at its tip, the Lido narrows down along its length until it is only a few hundred yards across. It is not one island; rather it is a whole string of them, artificially joined over the centuries to form a barrier protecting the city from the Adriatic. It was all but deserted, offering nothing to the population except uncertain weather in winter and a place to walk in summer.

And to swim; I had learned to swim as a boy when I stayed for the summers at the house of a relative in Hampshire. This family possessed a large garden with a fine pond, surrounded by reeds. Once you waded through them, you had the finest swimming place imaginable, with clear fresh water that warmed pleasantly in the sun. There my cousins had taught me to swim and, although I was not expert, I had learned also to love the feel of water. To see the rolling waves of the Adriatic basking in the sunshine of late summer gave me one thought only, which was to wade into the water as quickly as possible.

Again, the thought occurred to me; I had been sent to school at a boarding establishment in Brighton until I was thirteen, and had seen the bathing houses and the women ponderously wading into the icy water – for their health, I imagine, as it is difficult to see how it could have been for their pleasure – dressed in voluminous costumes so heavy they could not possibly have swum without sinking. I remembered also the habitually leaden skies, and the chill that hit you as you emerged from the water dripping wet, only to be frozen by the frigid winds of an English summer.

And here was something close to paradise on earth. Men now go to the South Seas to search for such an unspoilt landscape; back in 1867 it could be found much closer to home, only a short boat ride from San Marco.

'It's beautiful,' I said as we walked down a little path that led to a copse of trees.