‘There was always a crisis, a tension, but one knew that that’s what he lived on; the fuel that got him going. Which it did with any good politician,’ she adds, noting that the same was true for her husband. Did Churchill wear the pressure with equanimity? ‘Oh yes. Of course,’ she insists, as though nothing else would be possible. ‘Certainly.’ How did he cope? ‘I don’t know. But he had always done it.’ Did he drink too much? ‘No, not more than most men,’ she fires back.

I ask about her wartime visits to Chartwell: ‘I didn’t particularly like it, but it was interesting always because Winston was so interesting,’ she recalls. ‘One always wanted to know what he was thinking and doing.’ Whatever the house itself lacked in aesthetic quality (‘Have you ever seen it?’ she asks), its host more than made up for its architectural shortcomings. ‘It was just him,’ Avon states emphatically. ‘One went and there was him and nothing else. They had the lunch or whatever it was, and he would talk and one would listen; that was the important part.

‘But he was not interested in what anybody else had to say,’ Avon recalls, laughing fondly. That said, she insists that he was ‘very polite’. ‘If somebody famous was at lunch he would listen to them, but on the whole he didn’t pay any attention to anybody.’

Was he entertaining company, I ask; funny? ‘He was certainly witty…’ And somewhat terrifying at times? ‘Not in the least, no. But,’ she breaks into laughter, ‘I could see he was terrifying, but not to me, no.’ Avon also recalls that he was ‘very conscious about things like nieces and nephews’.

Marsh asked what her abiding memories of her uncle were:

All these years on, how does she remember him? ‘He was exceptional, certainly,’ she punctuates this with a frank chuckle. ‘I think I realised he was very great in spite of the fact that everyone kept telling one that he was.’ She raises her eyebrows. ‘I did realise that he was exceptional. You couldn’t not.’ The greatest prime minister of the twentieth century? ‘Who was greater?’ she answers.

Then he ventured into present-day issues:

What does she think Winston would make of modern Britain? Lady Avon looks over towards the tall windows momentarily. ‘Not much,’ she chirps. ‘I don’t know. He was very, very old-fashioned in his approach to life.’ That comment sits a moment; the quiet of the square seeps into the salon.

Where would Churchill be on Brexit, I ask? ‘I think he would probably not [be] very much for staying in Europe,’ she announces after some consideration. ‘But he was a good politician,’ she adds, ‘so I don’t know what he would have said.’ Which is rather a good answer when you think about it.

Then questions turned towards her late husband and the Suez Crisis:

I wonder how he saw it all; was he proud of his career?

‘I suppose so,’ she replies doubtfully. ‘Absolutely.’ Does she think people have the wrong sense of Suez – that it was a mistake? There’s a long pause. ‘A mistake because it took place at all?’ she asks. ‘I don’t know,’ she states at last. (At the time she famously said that she ‘felt as if the Suez Canal was flowing through my drawing room’.) I wonder if memories of this crisis have fallen prey to time, as she explains: ‘I’m not good at politics, I’m afraid.’ I’m still not sure as the silence of Bryanston Square returns.

How would Eden have liked to be remembered? ‘You mean as a success or failure?’ she responds. ‘Certainly [he] was a success at the beginning,’ she says, referring to his three spells as foreign secretary – covering ten years between 1935 and 1955 – before the disappointing period of highest office. ‘At the end, I suppose not. I never thought about it,’ she adds absently. She reaches forward to the plate and nudges a biscuit towards me. ‘Have that one,’ she says.

While being photographed for the article, she asked Marsh about his tie. So many British ties represent private club membership and other associations:

‘What does your tie represent?’ asks Lady Avon, looking over. It’s decorative, I say. ‘That’s disappointing. Right,’ she chirps, addressing Greg. ‘Where am I looking?’