The time is 7.30am and Buckingham Palace is starting to stir. The police sergeant sitting outside the Queen's bedroom is approaching the end of his overnight shift.
He used to go off duty at 6.30 — but after an intruder entered the bedroom at about seven one morning in 1982, when no one was on guard, the extra hour was added.
Her Majesty's personal maid walks towards him carrying the 'morning tray' for her royal mistress, reports Daily Mail.
On it are pots of Earl Grey tea and hot water, both in solid silver, cold milk but no sugar. The cup and saucer are bone china and there is also a fine linen napkin draped across the tray embossed with the royal cypher E II R.
The maid gives a light tap on the door, which bears the name 'The Queen' on a white card in a plain brass holder.
Prince Philip's set of rooms, just a few yards along the corridor, are workmanlike and functional, complete with a well-equipped barbershop that features a padded and fully adjustable barbershop chair, wash basin and a machine for heated towels.
One of London's leading barbers comes in once a week to trim the royal locks, though the Duke prefers to shave himself.
But, since his retirement from public duties, he spends most of his time these days at Wood Farm on the Sandringham Estate in Norfolk. So the Queen usually spends her working week alone in London.
The maid enters the Queen's bedroom and walks quietly across to the bedside table with its family photographs and telephone, complete with "panic button" — the one which was spectacularly ignored on that morning when intruder Michael Fagan became the only man, apart from her husband, to see the Queen asleep in bed.
The colour scheme of the room is pale green, the Queen's favourite shade.
Her maid switches on the Roberts radio which is tuned to BBC Radio 4, as the Queen likes to wake up to the sound of John Humphrys and his colleagues grilling unfortunate politicians on the Today programme.
Then, while Her Majesty is enjoying her first cup of tea, her maid will go into the adjoining bathroom to draw the bath, which has to be exactly the right temperature: tested with a wooden-cased thermometer, and no more than seven inches of water.
While the Queen is in her bath, one of her three dressers, under the supervision of Angela Kelly, the Queen's Personal Assistant and Curator of her Wardrobe, lays out the first outfit of the day in the adjacent dressing room with its floor-to-ceiling mirrors and walk-in wardrobes.
Mrs Kelly knows exactly what is needed, as she is given the Queen's daily programme the evening before. Depending on the day's engagements, the Queen may have to change as many as five times, but she rarely makes her own choice; that is what she pays her dressers to do, she says.
Once the Queen has dressed, her hairdresser brushes and arranges her hair in the style that hasn't changed in decades.
Breakfast is served promptly at 8.30 in the Queen's own private dining room. A footman has brought the food to a hot-plate — a silver "muffin dish" with the food on top and hot water underneath — and then he leaves the room so the Queen can eat in peace.
Meanwhile, a lone piper from one of the Scottish regiments prepares to march up and down on the terrace below.
The Queen loves the music of the bagpipes and every morning she listens to some of her favourite tunes.
By 9.30, the Queen will be at her desk in her sitting room cum office, ready for two solid hours of paperwork. The room is comfortable rather than luxurious, with armchairs and sofas upholstered in country-house-style chintz.
The desk is Chippendale and the Queen brought it with her when she moved from Clarence House in 1952. A heavy crystal double inkwell contains the black ink the Queen uses to sign official documents and the special green colour she likes for personal letters. She rarely uses a ballpoint pen, insisting on her favourite old fountain pen.
There's also a pristine sheet of blotting paper, replaced every day and black in colour so no one can read what she has written by holding it up to a mirror.
This is very much a working desk. As a former Page says: "It may appear cluttered and untidy to the average eye, but the Queen knows where everything is and hates it if anything is moved without her permission."
Her press secretary will have prepared a digest of the day's news from the early morning radio and television bulletins. Once she has read this and any other papers, she presses a button on the console in front of her.
The first person she calls is her private secretary. He is waiting in his office on the ground floor and when he hears the words, "would you like to come up?" he knows it's time to start the day's work. Carrying a small wicker basket containing the documents the Queen has to read and initial, he enters the room, gives a brief neck bow and says: "Your Majesty." Thereafter, he addresses her as "Ma'am".
The Queen's mailbox normally runs to scores of items every day, so she has mastered the knack of 'scanning' or speed-reading.
If guests are expected at the Palace, the housekeeper is summoned so that domestic arrangements for their comfort can be discussed.
Later in the morning, the duty lady-in-waiting is called to the sitting room. The Queen shows her some of the letters she has received which require a personal reply. Those from children and the elderly get special attention and the lady-in-waiting writes the letters and signs them on behalf of the Queen.
Personal friends who write to Her Majesty put their initials in the lower left-hand corner of the envelope and, when the staff see these, they know not to open them, for the Queen likes to open her personal mail herself.
Official guests, such as incoming or outgoing foreign emissaries coming to present their credentials or take their leave, have an audience at noon. This takes place in the Audience Room, also part of the Queen's suite, and lasts for around ten minutes.
Lunch is usually eaten alone, unless one of her four children is in the Palace. Prince Andrew sometimes joins his mother after being invited formally through the Queen's Page. Her Majesty prefers light meals, but although the dishes may be simple they are superbly presented — every sprout, carrot or potato exactly matching its neighbour in shape and size. And during the day she doesn't drink alcohol, sticking instead to her favourite still Malvern water.
The royal chef also sends a list to Her Majesty's Page, containing three suggestions for every meal during the coming week. It is returned when she has indicated what she wants.
And all menus continue to be written in French, having been the official language at Court since Queen Victoria's reign, when her French head chef insisted on French cuisine and the menus handwritten in that language.
Immediately after lunch, the Queen likes to walk in the gardens. Household staff know to keep well out of the way at this time: she doesn't welcome company or want to see anyone else in the gardens.
Then she relaxes for half an hour with the Sporting Life and Racing Post, the "bibles" of the racing fraternity. If she is at the Palace in the morning and there are engagements in the afternoon, they will be in the London area. When the Queen is ready to leave for them, her Page phones her personal police officer, in his office on the ground floor, to warn him to be waiting at the Garden Door with the car door open.
As Her Majesty walks downstairs — she only occasionally uses the ancient lift — a small knot of people materialises and wait to see her off. These are her private secretary and several of the household. They will also be there when she returns.
All afternoon engagements are scheduled to finish before 4.30 so that the Queen can be back at the Palace in time for tea at five.
It's an immovable feast and the meal she enjoys the most: tiny sandwiches without crusts, cut to a precise size, warm scones with cream and strawberry jam and, always, her favourite Dundee fruit cake. The ritual never changes and neither does the fare.
After tea, Her Majesty returns to her office for another hour. If there is no evening engagement, the Queen retires to her own rooms just after six to rest before dinner.
The exception is Tuesday evening, when the Prime Minister arrives for their weekly audience at 6.30. It used to be an hour earlier, but when Prince Charles and Princess Anne were children, the Queen liked to spend that time with them, so she changed the appointment to half past six — and it has remained so ever since.
As the meeting is official, it takes place in the Audience Room, on the north-west corner of the Palace between the Royal Closet and the Queen's dining room, and lasts for no more than half an hour.
Dinner for the Queen is the most relaxed meal of the day, sometimes eaten off a tray. She likes to remain in her private quarters, reading or watching television in the sitting room next door to her office.
Frequently, she spends part of the evening working on her "boxes" — the official dispatch cases which contain correspondence from government departments in the United Kingdom and the Commonwealth.
Every evening, a report on the day's proceedings in Parliament is delivered to her, written by the Vice-Chamberlain of the Household, a senior MP, and is invariably read by the Queen before she retires.
Her Majesty is not a late-night person: she is usually tucked in by 11pm, but likes to read in bed.
Her favourite relaxation is to read the latest Dick Francis racing novel and she is sent the first copy of every first edition, always in hard back. The tradition continues now that Dick's son Felix has taken over writing his father's bestsellers.
So, often, the last lights seen shining out of the north side of the Palace are those in her rooms. They are easy to identify; they are the only ones with bow windows, overlooking Constitution Hill.
And tomorrow, she will do it all again.