Gun salutes marking the death of Prince Philip, the Duke of Edinburgh, will take place in London, Cardiff, Belfast and Edinburgh as well as aboard some Royal Navy ships and in Gibraltar today.
Some 41 rounds will be fired at the locations around the UK at a rate of one shot per minute from midday.
Meanwhile, flags will fly at half-mast around the country.
Prince Philip dies – Live reaction from UK and around the world
The Duke had strong military links, including serving with the Royal Navy during the Second World War.
In a statement on the royal website, it was said: “The tradition of Gun Salutes being fired throughout the country to mark significant national events dates back to at least the eighteenth century, and there are historical records of salutes taking place as early as the 14th century when guns and ammunition began to be adopted more widely.
“Similar gun salutes were fired to mark the death of Queen Victoria in 1901.”
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Defence Secretary Ben Wallace said: “His Royal Highness Prince Philip, the Duke of Edinburgh was a constant supporter and ambassador of the armed forces.
“We celebrate his life of service and offer our condolences to Her Majesty the Queen and the Royal Family.”
Chief of the Defence Staff, General Sir Nick Carter said: “His Royal Highness has been a great friend, inspiration and role model for the armed forces and he will be sorely missed.
“The Duke of Edinburgh served among us during the Second World War, and he remained devoted to the Royal Navy and the armed forces as a whole.
“A life well lived, His Royal Highness leaves us with a legacy of indomitable spirit, steadfastness and an unshakeable sense of duty. From all of us who serve today and who have served, thank you.”
People are being encouraged to watch the salutes, which will be broadcast both online and on TV.
In London, the King’s Troop Royal Horse Artillery will fire at Napier Lines, Woolwich Barracks, in the southeast of the capital.
Six 13-pounder First World War field guns will be used – these same guns were also fired for the Duke’s wedding to the Queen and at her coronation in 1953.
A salute at the Tower of London will be carried out by the Honourable Artillery Company.
Cardiff Castle, Hillsborough Castle, Belfast, and Edinburgh Castle are some of the other locations where guns will be fired.
The HMS Diamond, HMS Montrose and HMNB Portsmouth will also salute, while the Royal Gibraltar Regiment will fire from the British overseas territory.
Due to the pandemic, the mass gatherings usually seen following the death of a senior royal are being discouraged by the palace and the government.
A virtual book of condolences is available on the Royal Family’s website.
Plans for the funeral and what happens next are expected to become clearer over the weekend and into the start of next week.
Despite the discouragement from authorities, people still gathered to lay flowers and pay tributes outside of Buckingham Palace and Windsor Castle on Friday.
Prince Philip died peacefully in his sleep on Friday morning at Windsor Castle, a few months before his 100th birthday.
His children paid tribute to him as the rock in the Queen and their family’s lives in a BBC tribute on Friday evening.
The Princess Royal said she would best remember her father as “always being there”, someone to help with a problem or bounce ideas off.
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She added: “I will best remember him as always being there and a person you could bounce off ideas, but if you were having problems you could always go to him and know that he would listen and try to help.”
The Prince of Wales said: “Well you know he didn’t suffer fools gladly, so if you said anything that was in any way ambiguous he’d say ‘make up your mind’.
“So perhaps it made one choose your words carefully.
“He was very good at showing you how to do things and would instruct you in various things.”