UK celebrates Queen's record breaking reign
The Queen has thanked well-wishers for their "touching messages" as she became Britain's longest-reigning monarch. We look back at today's events and celebrations throughout the UK.
From the outside the Queen's trip to the Scottish Borders had all the trappings of a typical working day at the office.
It featured the official opening of a major transport project, plaque unveilings, flag-waving schoolchildren and dignitaries nervously waiting in line to meet their head of state.
The Americans have a saying for it "Another day, another dollar" - but the Queen takes the job more seriously than that.
She has been criticised by some for never expressing an opinion, never doing anything to stand out in comparison with her forebears and so cannot be considered a "great" Queen.
But her public style is more subtle, she is an unobtrusive host who listens, puts people at ease and accepts their good wishes.
So she shook hands, collected posies, talked to schoolchildren and asked informed questions.
Underlying it all was the momentous fact that today she became the longest reigning monarch in British history.
By working as normal she demonstrated how she has dedicated herself to the role of Queen, and is not distracted by moments for the history books.
Her comments as she opened the new Scottish Borders Railway in Tweedbank highlighted how she felt, as she said the milestone was "not one to which I have ever aspired".
On the steam train that took the Queen and Duke of Edinburgh from the Scottish capital to Tweedbank, the head of state appeared at ease sitting by the window watching the countryside go by.
The royal couple warmed to long-retired train driver Walter Bell who joined them in their luxury carriage and recounted tales about the days the railway was powered by steam engines.
Philip urged him to go on with his stories about life on the tracks when Mr Bell thought he had talked too long, and the Queen told him they both had a "special day".
With a goodbye wave the Queen signalled that her working day was over and she travelled back to Balmoral - the royal home where Victoria was staying when she became the longest reigning monarch.
Another milestone is approaching for the Queen - her 90th birthday which she will celebrate next year.
With age comes perspective and she may realise that her legacy will lie not in the length of her reign but in important factors elsewhere.
Northern Ireland celebrations
Celebrations will started early on Wednesday morning in Northern Ireland with schoolchildren in Belfast singing her praises. ITV's Good Morning Britain programme broadcast live from a number of schools including Belfast Girls Model, during which pupils will sang the first verse of the national anthem.
On Wednesday evening Finance Minister Arlene Foster was due to host an event in Stormont to mark the record service.
The event is attended by the Lord Lieutenant of County Down, David Lindsay, and includes a display of important artefacts including a throne used by the Queen when she visited Parliament Buildings, the Coronation Vase; a specially commissioned piece of artwork made for the occasion of the coronation and various pictures relating the Queen's long reign.
Ms Foster said: "Her Majesty the Queen has been a fixed point in an ever-changing world. Throughout her long years of public service she has displayed a tireless devotion to our country and its people. At all times the Queen has carried out her duties with a warmth of spirit and a kindness of heart."
A special Evensong in St Anne's Cathedral in Belfast will also mark the occasion.
A prayer written for the occasion, approved by the Queen, will be said in churches and cathedrals across the UK.
In St Anne's, where Choral Evensong takes place almost every weekday, the music will reflect this historic milestone and will include the national anthem.
Her Majesty's Lord Lieutenant of Belfast, Fionnuala Jay-O'Boyle, will be among those expected to attend the service, which begins at 5.30pm.
Longest reigning monarch in British history
The Queen is now considered to be the longest reigning monarch in British history.
She has surpassed her great-great-grandmother Queen Victoria's record on the throne and has reigned for more than 23,226 days, 16 hours and 30 minutes.
The monarch, however, remains modest and matter of fact about the achievement.
Although she thanked the nation for their kind messages as she opened the Borders Railway in Tweedbank on the landmark day, she admitted that the milestone was "not one to which I have ever aspired".
She added: ''Inevitably a long life can pass by many milestones. My own is no exception.
"But I thank you all and the many others at home and overseas for your touching messages of great kindness.''
She is believed to have passed Victoria's record at around 5.30pm but the exact moment she became Queen is hard to calculate as George VI died in his sleep in the early hours of the morning, possibly at around 1am.
At this time of year, the Queen is usually enjoying her much-loved annual break at Balmoral, but she broke from her holiday to carry out duties to mark the historic occasion.
The 89-year-old monarch, with the Duke of Edinburgh at her side, spent the day travelling 40 miles on the railway with Scotland's First Minister Nicola Sturgeon, starting at Edinburgh's Waverley Station, stopping off at Newtongrange in Midlothian before carrying on to the Borders town of Tweedbank.
She delivered her short speech at her last stop, demonstrating her business as usual approach at the end by remarking: "So now to the business in hand. It is my very happy duty to declare the Borders Railway open."
The milestone is tinged with sadness for the Queen as the calculation of the length of her reign is linked to the death of her father George VI, on February 6 1952 when he was just 56.
There was no mention of Victoria in the Queen's address but she was notably wearing her diamond bow brooch, which originally belonged to her ancestor.
She smiled broadly and waved as she was greeted by delighted crowds in Edinburgh where she began her journey on the polished steam locomotive Union of South Africa with Philip, sitting in a private compartment of the ''Pegasus'' Pullman coach at a crisp white linen-covered table decorated with flowers.
In private, the Queen acknowledged the day's significance. Retired train driver Walter Bell, 88, from Edinburgh, who sat with the royal couple for part of the way, revealed: "She said to me we've both got a special day."
Normal service was suspended for a time in the House of Commons as MPs paid tribute, with Prime Minister David Cameron saying: "The Queen is our Queen and we could not be more proud of her.
"She has served this country with an unerring grace, dignity and decency and long may she continue to do so."
Ms Sturgeon told the Queen in a speech: "For those watching from around the world let me say, on their behalf ma'am a simple but heartfelt thank you.''
Afterwards, she described the Queen as being "in tremendous form".
Back at Balmoral this evening, the Duke and Duchess of Cambridge are joining the Queen for dinner, although it is understood the gathering is not to mark the longest reign.
The rest of the royals carried on with their scheduled engagements, with the Duchess of Cornwall describing the milestone as "marvellous" on a tour of the This Morning studios.
Heir to the throne and future king the Prince of Wales was filming a Prince's Trust documentary with Ant and Dec.
The Duke of York praised the Queen's consistency and leadership, but described the day as a "normal run of the mill sort of date. It's just one day in her reign."
Although celebrations are much more low-key than any of the Queen's jubilees, a flotilla of boats processed down the Thames led by the royal rowbarge Gloriana. HMS Belfast sounded a four-gun salute and the Massey Shaw fireboat shot jets of water across the river, while Tower Bridge lifted in recognition of the sovereign.
Westminster Abbey and other churches and cathedrals rang their bells in the monarch's honour, while London's BT Tower scrolled the message ''Long May She Reign''.
Belfast Telegraph Digital