At Whitehall's iconic Cenotaph memorial the monarch laid the first wreath to commemorate members of the Armed Forces who died fighting in all conflicts since the First World War.
In brilliant autumn sunshine senior members of the monarchy, Prime Minister David Cameron, military chiefs and thousands of watching spectators gathered to pay their respects.
When the first stroke of eleven sounded from nearby Big Ben Whitehall observed a two-minute silence only punctuated by the hum of distant London traffic.
The Duchess of Cambridge watched the sombre events from a balcony at the Foreign and Commonwealth building with other royal women - the first time she has attended a Remembrance Sunday service as a member of the monarchy.
Her thoughts may have turned to her grandfather Peter Middleton who trained Canada pilots during the Second World War in Calgary and died last year aged 90.
Defence Secretary Philip Hammond, who yesterday returned from visiting troops in Afghanistan, paid tribute to the country's Armed Services.
He said: "We know that public opinion of the Armed Services is at a record high, the Armed Services have acquitted themselves incredibly well, of course in Afghanistan on an ongoing basis - and also in the operation in Libya over the course of this year.
"The public hugely respects and admires what our service people do and the professionalism with which they do it, and we're here today to remember those who sadly have paid the ultimate price."
Forces in Camp Bastion, Britain's largest base in Afghanistan, and other military outposts across the world held their own services to pay tribute to past servicemen and women.
The fighting in the Middle East country claimed its latest life a few days ago, Territorial Army soldier Private Matthew Thornton, 28, of 4th Battalion The Yorkshire Regiment, was killed by an improvised explosive device while on patrol in Babaji, Helmand Province.
His death takes the number of British personnel who have died since operations began in Afghanistan in 2001 to 385.
Mr Hammond added: "From a military perspective it's clear that the British held area of Helmand is making very good progress, enemy initiated incidents are well down the situation on the ground is much more secure.
"But this can only be part of a broader political process, the government of Afghanistan has to create an environment in which everybody in Afghanistan can feel safe and secure."
Lieutenant General Sir John Kiszely Royal British Legion's National President highlighted how for many across the country Remembrance Sunday is a very personal event.
He said: "We've remembered those who fought for our freedom during the two World Wars, but also mourned and honoured those who have lost their lives in more recent conflicts.
"Today would've been a personal time for a lot of people, as we each remember loved ones, friends, comrades who have given their lives in service to the nation."
Relatives of those killed in the 1987 Remembrance Day IRA bombing in Enniskillen joined hundreds of others at the Co Fermanagh town's cenotaph for the annual commemoration event.
Stormont minister Arlene Foster and Ulster Unionist leader Tom Elliott were among dignitaries who laid wreaths after the two minute silence.
Eleven people were killed when the terrorist bomb exploded in a building beside the cenotaph 24 years ago in the minutes before the commemoration was due to start.
Services were held across Northern Ireland to mark Remembrance Day.
In London, the deafening sound of gunfire from the King's Troop Royal Horse Artillery stationed in Horse Guards Parade signalled the start of the two-minute silence as Big Ben chimed.
In the shadow of the Cenotaph the Queen stood motionless with her head bowed, at the head of her family who stood in a line behind her.
The group - all dressed in military uniform - were the Duke of Edinburgh, the Prince of Wales, the Duke of Cambridge, the Duke of York, the Earl of Wessex, the Princess Royal and the Duke of Kent.
Close by was Mr Cameron, Liberal Democrat leader Nick Clegg, Labour leader Ed Miliband, leaders of other parties, High Commissioners from Commonwealth countries and defence chiefs.
The crowds, who numbered in their thousands and contained many veterans, also watched in silence.
Another booming artillery fire echoed around Whitehall as the silence came to an end.
As the artillery blast faded, Buglers of the Royal Marines sounded the haunting melody of The Last Post - which traditionally signalled the end of a soldier's day.
The Queen led the laying of the wreaths and was followed in seniority by the other royals - Philip, Charles, William, Andrew, Edward, Anne and Prince Edward - the Duke of Kent.
Prince Harry was missing as he is in America on the final stage of his Apache helicopter training. He instead attended his Army Air Corps squadron's remembrance service parade in Arizona.
Kate was joined on the Foreign and Commonwealth balcony by the Duchess of Cornwall, the Countess of Wessex and Vice Admiral Sir Timothy Laurence, the husband of the Princess Royal.
The Duchess of Cambridge was dressed in black like the other royals and wore two bright red poppies and a bowler style hat.
The members of the monarchy were followed by the politicians and other dignitaries who laid their floral tributes.
In Hampshire, around 1,000 people gathered outside Winchester Cathedral for a service and silence.
Local dignitaries, including the city's MP Steve Brine, and veterans from the Second World War laid wreaths at the war memorial outside the west front of the cathedral.
Scottish First Minister Alex Salmond led tributes north of the border.
He laid a wreath during a service at the Stone of Remembrance on Edinburgh's Royal Mile and attended a Service of Remembrance at the city's St Giles Cathedral.
He said: "Remembrance Sunday is the time when every man, woman and child in Scotland should pause and give thought to the immense sacrifice which so many have made to protect our way of life and freedom.
"This moment of reflection is a small but significant tribute to all of our servicemen and women, past and present, who have paid the ultimate price in defence of our country.
"Today is a day to proudly remember the bravery of all those who have given their lives in the service of our nation and whose sacrifice will never be forgotten."
A two-minute silence was also observed at an event at the Cenotaph in Glasgow's George Square.
Representatives of the Royal British Legion paid tribute there to the dead, along with council leader Gordon Matheson, Deputy First Minister Nicola Sturgeon and Scottish Tory leader Ruth Davidson.
A Guard of Honour was provided by The Royal Highland Fusiliers, the 2nd battalion of the Royal Regiment of Scotland.
Perth staged its annual civic Remembrance Sunday parade and church service, beginning at the council buildings on High Street.
In Aberdeen, a remembrance ceremony was held at the war memorial at Cowdray Hall, Schoolhill.
Lord Provost Peter Stephen led the laying of wreaths at the memorial.
He said: "Remembrance Sunday is a time to reflect on the sacrifices made by so many in the past for the benefit of others and to remember the men and women currently serving in the Armed Forces and their families."
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