Soon, wetlands gave way to farmland that was patched with pine woods, with paddocks and flint cottages. Below them, briefly, was the shell-pink Regency villa at Abbottswood, where she was surprised to see a herd of deer ambling slowly across the lawn. Next came the stubbly, immaculate fields and scattered copses of the Muncaster Estate, whose furthest reaches bordered one of the royal farms, and then at last the fields, dykes and villages of the Sandringham Estate itself. As the helicopter made its turn, the Queen saw a glint of seawater in the distant Wash and a minute later Sandringham House appeared behind a ridge of pines, with its formal and informal gardens, its lakes and its sweeping lawns amply big enough for them to land.

This close to Christmas, Rozie didn’t expect to have much to do. With no monasteries to dissolve or royal marriages to broker, the main job of the Private Office was to liaise with the Government, manage communications and organise the Queen’s public schedule. But Whitehall and Downing Street had effectively shut down for the holidays; the media were fixated on holiday stories; the Queen’s next public event was in three weeks, and even that was only a tea party in the village. Thomas Cromwell would have found it all very tame. Rozie had mostly been catching up with the residue of emails that had somehow never made the ‘urgent’ list in her inbox. However, an hour ago a new one had come in. Perhaps this break wasn’t going to be as quiet as she’d anticipated, after all.

Lined up outside the entrance hall, Mrs Maddox, the immaculate housekeeper, and her team were waiting to welcome the royal couple back. Today, the interior smelled deliciously of woodsmoke from the fire that popped and crackled in the saloon behind them, where the family would gather later for drinks and games. The dogs happily padded inside, keen to be back, while Philip took himself straight off to bed.

The Queen had just enough energy to do justice to a couple of freshly made mince pies and a pot of Darjeeling in the light and airy drawing room at the back of the house, whose large bay windows overlooked the lawn. In one of the bays a Christmas tree was already in place, its branches partly decorated on a red and gold theme, ready to be completed when the rest of the family arrived tomorrow. Normally, she chose the tree herself, but this year there hadn’t been time. A small price to pay for a cosy afternoon indoors, which she very much needed.

She had just finished talking to Mrs Maddox about the next few days’ arrangements when Rozie appeared at the drawing room door. As her efficient APS curtsied, the Queen noticed that, rather ominously, she held a closed laptop under her arm. ‘Your Majesty, do you have a moment?’

‘Is there a problem?’ the Queen asked, hoping there wasn’t.

‘Not exactly, but there’s something you ought to know about.’

‘Oh, dear.’ They caught each other’s eye, and the Queen sighed. ‘The small drawing room, I think.’

She led the way to the room next door, whose floral, silk-lined walls gave it a gentle, feminine air, somewhat in contrast to the lively bird sculptures that Prince Philip chose to keep there: reminders of one of his chief pleasures of the estate.

Rozie closed the door behind them. The Queen looked up at her. Rozie, a striking young woman of thirty, was over six feet tall in her signature heels. At her age, and at a shrinking five foot two, the Queen was used to looking up at almost everybody . . . figuratively speaking. She didn’t find it problematic, except when she had to shout up at tall, deaf dukes and ministers. Fortunately, her APS’s hearing was excellent.

‘All right. What is it? Nothing to do with the new president?’

‘No, ma’am. The police have been in touch. I’m afraid there’s been a discovery.’

‘A hand was found yesterday morning, in the mudflats at Snettisham Beach.’

The Queen was startled. ‘A human hand?’

‘Yes, ma’am. It was washed up by a storm, wrapped in a plastic bag.’

‘My goodness. No sense of where it came from?’

‘Ocado, ma’am, since you ask. They deliver food from Waitrose.’

The APS frowned. ‘Not yet. They hope to identify the victim soon. One of the fingers was wearing an unusual ring, which may help.’

Rozie shook her head. ‘A man’s. It’s a signet ring.’

At last, the Queen understood the presence of the laptop. Sir Simon would have come without it, but fortunately – in the circumstances – he wasn’t here. Her private secretary liked to spare her any ‘unpleasantness’. But after ninety years, an abdication, a world war, the early loss of her father and a rich selection of family scandals, she was more capable of dealing with unpleasantness than most. Rozie was more realistic. Women understood each other, the Queen found. They knew each other’s strengths and weaknesses, and didn’t underestimate the strengths.