Diamond Jubilee: Queen celebrating 60-year reign
The Queen is to mark the 60th anniversary of her becoming the monarch of the UK and Commonwealth later.
The milestone will be marked by several events in the coming months, with the main celebrations taking place in June.
In a Diamond Jubilee message, the Queen said she felt "deeply moved" by the support shown for the anniversary.
She usually spends Accession Day - the day her father, George VI, died in 1952 - privately but, this year, she has two engagements planned in Norfolk.
This year's anniversary will be marked by visits to King's Lynn Town Hall and the nearby Dersingham Infant and Nursery School.
Crowds are expected to gather to greet the Queen, despite the cold conditions.
Two official photographs will also be released later and a 41-gun salute will be held in Hyde Park, London, followed by a 62-gun salute at the Tower of London.
For the Queen, this is a day of celebration - her great-great grandmother Victoria was the only other British monarch to achieve this milestone - and commemoration, marking as it does the anniversary of the death of her beloved father, George VI.
So, a significant moment will pass in a deliberately low-key manner with a visit to a town hall and a primary school in Norfolk.
As the weather improves and the months go by, there will be nothing subdued about the events which will be staged for a reign which is the second longest in British history.
Her close friend, Lady Penn, told the BBC the Queen had been the "still small voice of calm" in a social revolution in this country over the past 60 years.
In her Diamond Jubilee message, with the words "I dedicate myself anew to your service", the Queen is repeating a pledge she first made at the age of 21.
This is a royal octogenarian who intends to remain as Sovereign for as long as she lives.
During her reign the Queen has seen 11 prime ministers come and go, with David Cameron her 12th.
Mr Cameron praised the "magnificent service" given by the Queen and called her a "source of wisdom and continuity".
"With experience, dignity and quiet authority she has guided and united our nation and the Commonwealth over six varied decades," he said.
One former Prime Minister, John Major, reflected on the counsel of the Queen and the many private meetings he had with her during his premiership during an interview on BBC One's Andrew Marr Show on Sunday.
He said: "Most of the present cabinet weren't born when the Queen became monarch. So there's very little she hasn't seen, very little she doesn't understand. And anyone who doesn't listen to her view and consult her when necessary is missing a huge opportunity."
Meanwhile, Sir John has formally launched the Queen Elizabeth Diamond Jubilee Trust to help those in need across the Commonwealth.
He will chair the grant-making body, which will focus on areas such as fighting curable diseases and the promotion of education and culture.
A set of six 1st class definitive stamps, all of which feature official portraits of the Queen, are also being issued to mark the monarch's milestone.
Moya Greene, Royal Mail's chief executive, said: "The Queen's image is one of the most recognisable in the world and we are delighted to bring these iconic images together to mark the 60th anniversary of the Queen's accession."
The Diamond Jubilee Miniature Sheet marks the first occasion on which official images of the monarch, sourced from stamps, coins and banknotes, have been brought together for a stamp issue.
The Queen's 60 years as monarch are set to be marked by a series of regional, national and international events during 2012, culminating in a four-day long UK Bank Holiday weekend in June.
Events planned to take place during the summer include the Queen leading a flotilla of a thousand boats along the Thames and a chain of beacons being lit across the country.
The Queen and the Duke of Edinburgh also intend to travel as widely as possible across the UK.
Other members of the Royal Family will visit the 15 other countries where the Queen is head of state, as well as some other Commonwealth countries.
Key public events
- River Thames, London; 3 June - More than 1,000 private boats will escort the Queen on a specially designed royal barge down the River Thames
- Windsor Castle, Berkshire; 10, 11, 13 May - Three evening performances featuring military and equestrian displays, music and dancing from around the world
- St Paul's Cathedral, London; 5 June - There will be a service of thanksgiving at St Paul's Cathedral and a formal carriage procession by the Queen
In her message to mark the anniversary, the Queen said: "I am writing to thank you for the wonderful support and encouragement that you have given to me and Prince Philip over these years and to tell you how deeply moved we have been to receive so many kind messages about the Diamond Jubilee.
"In this special year, as I dedicate myself anew to your service, I hope we will all be reminded of the power of togetherness and the convening strength of family, friendship and good neighbourliness, examples of which I have been fortunate to see throughout my reign and which my family and I look forward to seeing in many forms as we travel throughout the United Kingdom and the wider Commonwealth."
The Duke and Duchess of Cambridge will visit Malaysia, Singapore, the Solomon Islands and Tuvalu.
The Prince of Wales and Duchess of Cornwall will visit Australia, Canada, New Zealand and Papua New Guinea.
Prince Harry will tour Belize, Jamaica and the Bahamas.