Commenting on the contrast seemed to be a good way to get the conversation started and to introduce an interesting topic on which I was knowledgeable. I was careful to attribute the research to Gene to avoid appearing egotistical.

Despite my not using any pejorative words for height and weight, Lydia responded in a manner that appeared cold.

‘To begin with, Don, we’re not a couple. We just met outside the restaurant.’

Seymour was more helpful. ‘Isaac and Judy invited us separately. Judy’s always talking about Lydia, so it’s great to meet her at last.’

‘I’m in Judy’s book club,’ said Lydia, addressing Seymour rather than me. ‘Judy’s always telling us stories about you.’

‘Good ones, I hope,’ said Seymour.

‘She says you’ve improved since your divorce.’

‘People should be forgiven everything they do three months either side of a divorce.’

‘On the contrary,’ said Lydia. ‘That’s exactly what they should be judged on.’

Lydia’s information that they were merely two people who had coincidentally been invited to the same lunch was in line with Gene’s theory. It gave me an opportunity to reenter the conversation.

‘A victory for evolutionary psychology. The theory predicts that you would not be attracted to each other; I observe evidence that is counter to the theory; more detailed examination of the data supports the theory.’

I was not seriously offering a scientific analysis, but using scientific language for the purpose of amusement. I have considerable experience with the technique, and it usually results in some level of laughter. In this case it did not. If anything, Lydia’s expression became less happy.

Seymour at least smiled. ‘I think your hypothesis rests on some invalid assumptions,’ he said. ‘I’ve got a bit of a thing for tall women.’

This seemed like very personal information. If I had shared what I found physically attractive about Rosie, or women in general, I am sure it would have been judged as inappropriate. But people with better social skills have more leeway to take risks.

‘Luckily,’ Seymour continued. ‘Or I’d be limiting my options in a big way.’

‘You’re searching for a partner?’ I asked. ‘I recommend the internet.’ My extraordinary success in finding the perfect partner as a result of random events did not invalidate the use of more structured approaches. At this point, Isaac and Judy arrived, increasing the conversational complexity by a factor of 3.33 but improving my comfort level. If I had been left alone with Seymour and Lydia for longer, I would probably have made some sort of social error.

We exchanged formulaic greetings. Everyone else ordered tea, but I concluded that if I had made a mistake in drinking sake, it was too late to recover, and ordered a second flask.

Then our waiter brought the menu. There was an array of fascinating food, consistent with the research I had undertaken on the restaurant, and Judy suggested we order one plate each and share. Excellent idea.

‘Any preferences?’ she asked. ‘Isaac and I don’t eat pork, but if someone else wants to order the gyoza, that’s fine.’ She was obviously being polite, and ordering the gyoza would have made their meals less interesting than the others due to reduced variety. I did not make that mistake. When my turn came, I took advantage of Rosie’s absence to try something that would normally have provoked an argument.

‘The bluefin tuna sashimi, please.’

‘Oh,’ said Lydia. ‘I didn’t see that. Don, you might not be aware that bluefin is an endangered species.’

I was aware of this fact. Rosie ate only ‘sustainable seafood’. In 2010, Greenpeace had added the southern bluefin tuna to its seafood Red List, indicating a very high risk of it being sourced from unsustainable fisheries.

‘I know. However, this one is already dead and we will only be sharing a single portion among five people. The incremental effect on the world tuna population is likely to be small. In exchange we have an opportunity to experience a new taste.’ I had never eaten bluefin tuna and it had a reputation for being superior to the more common yellowfin, which is my favourite food component.

‘I’m up for it, as long as it’s definitely dead,’ said Seymour. ‘I’ll skip my rhino horn pills tonight to make up.’

My mouth was open to comment on Seymour’s extraordinary statement but Lydia spoke first, giving me time to consider the possibility that Seymour was making a joke.

‘Well, I’m not up for it,’ she said. ‘I don’t accept the argument that individuals can’t make a difference. That’s the attitude that’s stopping us doing anything about global warming.’

Isaac offered a useful if obvious contribution. ‘Plus the Indians and Chinese and Indonesians wanting to have our standard of living.’

Lydia may or may not have agreed. But she was talking to me.

‘I suppose you don’t think about what sort of car you drive or where you shop.’

Her supposition was incorrect, as was the implication that I was environmentally irresponsible. I do not own a car. I ride a bike, use public transport or run. I have relatively few clothes. Under the Standardised Meal System, only recently abandoned, I had virtually zero waste in food and I now treated the efficient use of leftovers as a creative challenge. But I consider my contribution to reducing global warming negligible. My position on rectifying the problem seems to be unattractive to many environmentalists. I had no desire to spoil our lunch with unproductive arguments, but Lydia seemed to be already in irrational greenie mode, so, as with the sake, there was no point in holding back.