WORLD leaders, royalty and hundreds of veterans will honour those who fought in the D-Day landings 75 years ago during a national commemoration ceremony.

The Queen will be joined by Prime Minister Theresa May and US president Donald Trump alongside 300 veterans in Portsmouth on Wednesday to mark the forthcoming anniversary.

Some 60,000 members of the public are expected to attend the Portsmouth Naval Memorial on Southsea Common for the event which marks the 75th anniversary of the biggest amphibious invasion in military history.

Considered a turning point in the Second World War, Operation Overlord saw thousands killed and injured after it launched on June 6 1944.

South Wales Argus:

(D-Day veterans gather under the 'Embracing Peace' statue, during a D-Day event at Portsmouth Historical Dockyard. Picture: Andrew Matthews/PA Wire.)

Mrs May will be making her final official appearances as the British Prime Minister during the D-Day commemorations which continue on Thursday across Normandy.

Meanwhile, hundreds of veterans are flocking to northern France and Portsmouth as well as to events around the country to mark the occasion.

On Wednesday Mrs May will host 15 world leaders and representatives in the Hampshire port city.

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The event will be the first time the UK has hosted this many world leaders outside a formal summit since the 2012 Olympics.

A mass security operation has been launched in the wake of Mr Trump's attendance at the event - as part of his UK state visit.

Some critics have claimed his presence draws focus away from the veterans.

South Wales Argus:

(D-Day veteran Bert Turner releases a dove with other D-Day veterans following a dedication for the D-Day memorial flotilla, at Portsmouth Historical Dockyard. Picture: Andrew Matthews/PA Wire.)

Representatives from every country that fought alongside the UK in Operation Overlord - the Battle of Normandy - will attend commemorations as well as The Prince of Wales, members of the armed forces and the veterans who are all over 90 years old.

Joining Mrs May will also be French president Emmanuel Macron, the German chancellor Angela Merkel as well as prime ministers from Canada, Australia, New Zealand, Belgium, Czech Republic, Greece, Luxembourg, The Netherlands, Norway, Poland, Slovakia and Denmark.

An hour-long production telling the story of the invasion will be played to the crowds featuring testimony from veterans before theatrical performances, live music as well as a flypast of the Red Arrows and Spitfires take place.

As part of the performance Mrs May will read a letter written by Captain Norman Skinner of the Royal Army Service Corps to his wife Gladys on June 3 1944. The letter was in his pocket when he landed on Sword Beach on June 6 1944. He was killed the next day, leaving behind his wife and two young daughters.

South Wales Argus:

(The ship Le Boreal sails along the Caen Canal through the Pegasus Bridge in Normandy, France, ahead of the anniversary of D-Day. Picture: Owen Humphreys/PA Wire.)

Afterwards world leaders will meet to discuss the western alliance and security after a reception with veterans.

From the deck of the aircraft carrier HMS Queen Elizabeth, Mrs May and Defence Secretary Penny Mordaunt will wave off the crowds of veterans who are set to retrace the journey they made across the channel 75 years ago. This time they will be followed by a flotilla of Royal Navy vessels.

More than 4,000 personnel will be involved in D-Day events in the UK and France, in what is set to be one of the biggest mobilisations of the UK Armed Forces in recent history.

Later in the afternoon veterans Harry Read, 95, and John Hutton, 94, will parachute into Normandy in honour of comrades they lost when they first made the descent 75 years ago.

Alongside around 280 paratroopers they will take part in the jump onto fields at Sannerville - the drop zone for the 8th Midlands Parachute Battalion during D-Day.

In the evening, a vigil and silent march will take place at Pegasus Bridge which was the scene of a 15-minute skirmish to take hold of the pathways over the Caen Canal and River Orne. This was one of the first places British troops liberated on D-Day.