The Queen has been moved to tears as the three most senior working royals attended a commemoration to mark the 80th anniversary of the historic D-Day military operation.

The King gave his first major address since his cancer diagnosis at the ceremony in Portsmouth, the main departure point for the 5000 ships that headed to Normandy on June 5, 1944.

Prince William was also there and greeted war veterans.

He told a war hero who inquired about his wife Kate, who is battling cancer, that “she is better, thanks. She would’ve loved to be here today”.

It was a rare public outing for the three working royals since the King began treatment for an undisclosed form of cancer and the Princess of Wales announced she was having chemotherapy.

The Queen appeared emotional and was photographed with tears welling in her eyes as Royal Navy serviceman Eric Bateman spoke about losing his best friend on the beaches of Normandy.

The King was also seen wiping his eye.

The Prince of Wales was the first to take the mic, followed later by the King’s poignant address.

“Today we come together to honour those nearly 160,000 British, Commonwealth and Allied troops who, on 5th June 1944, assembled here and along these shores to embark on the mission which would strike that blow for freedom and be recorded as the greatest amphibious operation in history,” the King said.

“As we give thanks for all those who gave so much to win the victory, whose fruits we still enjoy to this day, let us, once again, commit ourselves always to remember, cherish and honour those who served that day and to live up to the freedom they died for.”

About 4400 Allied troops died on D-Day.

“We will always remember those who served and those who waved them off,” Prince William said.

“The mothers and fathers, brothers and sisters, sons and daughters who watched their loved ones go into battle, unsure if they would ever return.”

An emotional letter written to his wife by a soldier killed the day after D-Day was read out.

King Charles wipes his eye on the emotional day. Photo: AAP

Prime Minister Rishi Sunak read out the message from General Bernard Montgomery, commander of the Allied forces on D-Day. It was delivered to all troops ahead of the invasion.

Meanwhile in France, where the main ceremonies will be held on Thursday with world leaders including US President Joe Biden and Ukrainian President Volodymyr Zelensky, thousands of tourists could be seen alongside the D-Day beaches and visiting World War II cemeteries.

Collectors drove army jeeps and US, Canadian, British and French flags adorned buildings.

“It’s very important not to forget this sacrifice,” British tourist Daniel Reeves, 27, said as he visited the US war cemetery in Colleville-sur-Mer earlier this week.

It’s “absolutely amazing and extremely emotional, especially when you see them, the veterans, and they say: Thank you my friend,” British visitor Karen Swinger said.

French President Emmanuel Macron, who earlier paid tribute to French resistance fighters in Brittany, will later take part in a ceremony in Saint-Lo, Normandy. It was almost entirely destroyed by Allied bombardments as part of D-Day and the Battle of Normandy.

“This trauma turned our city into the ‘capital of the ruins’, as playwright Samuel Beckett wrote,” the city’s mayor Emmanuelle Lejeune told Reuters.

The city of 12,000 people at the time was 90 per cent destroyed.