The Duke of Edinburgh has died “peacefully” in his sleep at the age of 99, leaving the Queen and her family “mourning his loss”.

Philip, famously described by the Queen as her “constant strength and guide”, died on Friday morning at Windsor Castle, a few months before his 100th birthday.

Buckingham Palace announced the duke’s death just after midday on Friday, issuing a statement that spoke about the royal family joining with people across the globe to grieve.

A man known as much for his keen interest in engineering and science as his outspoken comments and gaffes – he was central to the monarch’s life.

Philip became an international figure when he married the Queen more 70 years ago, and his death was marked with tributes from world leaders, foreign royal families and charities he supported.

The palace said in a statement: “It is with deep sorrow that Her Majesty the Queen announces the death of her beloved husband, His Royal Highness the Prince Philip, Duke of Edinburgh.

“His Royal Highness passed away peacefully this morning at Windsor Castle.

“Further announcements will be made in due course.

“The Royal Family join with people around the world in mourning his loss.”

No further details were released about the circumstances of his death.

The Queen may give a televised address in memory of her late husband but details of any possible broadcast have yet to be confirmed.

The Duke and Duchess of Sussex paid tribute to Philip on the website of their foundation Archewell, replacing its homepage with a memorial site and the words: “In loving memory of His Royal Highness The Duke of Edinburgh 1921-2021

“Thank you for your service…You will be greatly missed.”

In a tribute recorded for ITV News before Philip’s death, the Princess Royal said about her father’s legacy: “Without him life will be completely different.

“But from society’s perspective he was able to keep pace with the kind of technological changes that have such an impact… but above all that it’s not about the technology it’s about the people.”

The Prince of Wales visited his mother the Queen during Friday afternoon travelling from his Gloucestershire home to Windsor Castle, sources have said.

The announcement of Philip’s death reflected tradition and modern times, with the statement tweeted on the royal family account and also a framed notice attached to the railings of Buckingham Palace for a short period.

Prime Minister Boris Johnson was one of the first national figures to pay tribute to the duke – the longest-serving consort in British history.

Speaking from a podium in Downing Street, Mr Johnson said: “He was an environmentalist, and a champion of the natural world long before it was fashionable.

“With his Duke of Edinburgh awards scheme he shaped and inspired the lives of countless young people and at literally tens of thousands of events he fostered their hopes and encouraged their ambitions.

“We remember the duke for all of this and above all for his steadfast support for Her Majesty the Queen.”

US President Joe Biden highlighted the duke’s “decades of devoted public service”, Second World War service and environmental efforts in remembering his legacy.

He said in a statement: “Over the course of his 99-year life, he saw our world change dramatically and repeatedly. From his service during World War II, to his 73 years alongside the Queen, and his entire life in the public eye – Prince Philip gladly dedicated himself to the people of the UK, the Commonwealth, and to his family.”

During the lockdowns, Philip stayed at Windsor Castle with the Queen for their safety, alongside a reduced household of staff dubbed HMS Bubble.

The couple are thought to have spent more time together during the past 12 months, shielding from coronavirus, then they would in a normal year – a throwback to the early years of their marriage.

Windsor has become the focus of royal fans wanting to pay their respects but they are being encouraged by Buckingham Palace to donate to a charity they support or one Philip was associated with, rather than leave flowers or gather in groups at royal homes.

An online book of condolence has been opened on the royal family’s official website so the public can post their personal tributes.

Philip helped draw up the details of his funeral and was determined there should be a minimum of fuss.

It has long been known the Queen has final approval of the plans, which are expected to be announced in the coming days.

Harry, who laid bare his rift with members of his family during his Oprah Winfrey interview, is likely to attend his grandfather’s funeral, but it is not known if he will be joined by wife Meghan – who is pregnant.

Buckingham Palace has said Covid will affect any funeral plans: “During the coronavirus pandemic, and in light of current Government advice and social distancing guidelines, modified funeral and ceremonial arrangements for His Royal Highness the Duke of Edinburgh are being considered by Her Majesty The Queen. Details will be confirmed in due course.

“With the safety and wellbeing of the public in mind, and in accordance with Government guidelines, members of the public are asked not to gather in crowds. Those wishing to express their condolences are asked to do so in the safest way possible, and not to gather at Royal Residences.”

Philip’s funeral is expected to take place at St George’s Chapel, Windsor, but during England’s national lockdown, services can only be attended by a maximum of 30 people.

Union flags have been flying at half mast at all royal residences as a mark of respect and Westminster Abbey – where the Queen and Philip married on November 20, 1947 – tolled its tenor bell once every 60 seconds, 99 times, during Friday evening.

A period of mourning is expected and any planned official royal events that fall within this period are likely to be postponed.

Tributes have flooded in from around the world, including from Australian Prime Minister Scott Morrison, Irish Premier Micheal Martin, the Prime Minister of the Netherlands Mark Rutte, and Indian Prime Minister Narendra Modi.

European royal families remembered Philip as a “great friend” who “never ceased to leave an unforgettable impression”, with King Carl XVI Gustaf of Sweden hailing the duke as “an inspiration to us all”.

Justin Welby, the Archbishop of Canterbury, said Philip was an “outstanding example of Christian service”, adding: “On the occasions when I met him, I was always struck by his obvious joy at life, his enquiring mind and his ability to communicate to people from every background and walk of life.

“He was a master at putting people at their ease and making them feel special.”

The Cabinet met at 5pm on Friday to pay tribute to the duke and Parliament will be recalled from its Easter recess on Monday, a day earlier than its scheduled return.

The death of the duke comes in the midst of the worst public health crisis for generations as the UK and countries around the globe reel from the devastating impact of the coronavirus pandemic.

It has also taken place in the aftermath of Harry and Meghan’s bombshell Winfrey interview which left the monarchy in crisis after Meghan accused an unnamed royal of racism and the institution of failing to help her when she was suicidal.

Philip had returned to Windsor Castle on March 16 to be reunited with the Queen after spending a month in hospital – his longest ever stay.

He initially received care for an infection but then underwent heart surgery for a pre-existing condition.

The duke had looked gaunt as he was driven away from King Edward VII’s Hospital in central London, having been pushed in a wheelchair to the waiting car.

Philip – father to the Prince of Wales, the Princess Royal, the Duke of York and the Earl of Wessex – was just two months away from his 100th birthday in June.

He briefly stepped out of retirement in July 2020 when he carried out a rare official public engagement at Windsor.

The duke looked in fine form as he made his way down the steps to the castle’s quadrangle for a socially distanced ceremony to hand over his Colonel-in-Chief of The Rifles role to the Duchess of Cornwall, who was almost 100 miles away at Highgrove.

He showed he had lost none of his mischievous sense of humour when he joked with one of the soldiers about their fitness levels.

In April 2020, the duke released his first major statement since his retirement, praising key workers including refuse and postal staff, for keeping essential services running during the pandemic.

He was also pictured with the monarch at the Berkshire castle to mark his 99th birthday on June 10, at the secret lockdown wedding of his granddaughter Princess Beatrice on July 17 and with the Queen to mark their 73rd wedding anniversary in November.

The Queen and Philip spent a quiet Christmas in 2020 at Windsor alone, except for their staff, and Buckingham Palace announced on January 9 2021, during England’s third national lockdown, that they had both received their Covid-19 vaccinations.