‘I take all my guests on this particular carriage ride before they leave Balmoral,’ the Queen continued. ‘It gives glimpses of the memorial cairns that, as a family, we have built over the years. I am far too old and lame now to leave the carriage and climb up to them, for they have all, of course, been built on high crags, but I like to have sightings of them from the road. The first cairn we will come to is on the top of Craig Gowan and was built to celebrate our buying of the estate. I placed the first stone, then Albert laid one and then all the children laid a stone, in accordance with their ages. After that, everyone who had climbed up to the crag with us laid a stone. When the cairn was eight or nine feet high, Albert climbed to the top of it and, to cheers, my darling laid the last stone in place.’

Not for the first time May was struck at the intimate freeness of the Queen’s reminiscences. When sharing her experience of seeing Albert for the first time she had said, as if she was a young girl sharing a close confidence, ‘And I loved him at first sight. It was a coup de foudre, instant and undeniable, for Albert was more than handsome. Albert was beautiful.’

After Craig Gowan the next two cairns, Lenchen’s and Louise’s, were sited almost within sight of each other. ‘Although the plaque says Helena, not Lenchen,’ the Queen said. ‘The German form of Helena would not have been suitable on a plaque such as this, which was built to mark her marriage to dear Christian.’

As the carriage rocked to a halt at the best viewpoint, she said, ‘Christian is a prince of Schleswig-Holstein, and seeing his and Lenchen’s cairn has reminded me that Prince Ernst of Schleswig-Holstein made a proposal of marriage to you a little while ago; a proposal that, to my very great surprise, you did not accept. Was your refusal because, as an only daughter, you had no wish to live so far away in Germany?’

May’s tummy muscles tightened. She could let the Queen believe her assumption was correct, or she could tell her the truth. She took a deep, steadying breath. ‘I had met Prince Ernst some time ago at Marie-Louise’s birthday party and I . . . I felt no attraction for him and was sure we were not compatible. That was the reason I didn’t accept his proposal.’

The Queen pursed her lips and was silent for so long that May was terrified she was going to be asked to step down from the carriage and walk all the way back to Balmoral.