There were concerns ahead of the UK’s official D-day commemoration that the presence of Donald Trump and the circus that surrounds him would overshadow the most important people – the veterans and their families.

The worries were unfounded. At every point of a very long and emotional day the amazing stories and spirit of the 300 or so ageing veterans at the event in Portsmouth – and memories of those who did not make it back 75 years ago – took centre stage.

Men such as John Jenkins, 99, from Portsmouth, a platoon sergeant with the Royal Pioneer Corps on D-day, stole the show. Like many of his comrades, he said his lasting memories were of fear. “I was terrified, I think everyone was,” he said. “You don’t show it, but it was there.” He also said what happened was a big part of the man he became.

“I look back on it as a big part of my life. It changed me in a way. I was a small part in a big machine. You never forget your comrades, because we were all in it together. We must never forget.”

Facebook Twitter Pinterest The Queen and Theresa May greet the Canadian prime minister, Justin Trudeau. Photograph: Jack Hill/Reuters

Video recordings were played during the official commemoration event on Southsea Common of other men who were at D-day. Bob Roberts, a Canadian veteran, recalled the moment he and his colleagues were told they were about to be given live ammunition. “That was the first we knew we were in action. I thought ‘My God, I was never brought up to be killing people’. There were so many cases where I could have lost my life. I don’t know how I survived.”

After the commemorations on the common, the Queen, Trump and his wife, Melania, met veterans at a reception.

Thomas Cuthbert, a 93-year-old, who was in a landing barge oiler anchored off Utah and Omaha beaches, jokingly told the US president: “If only I was 20 years younger” while pointing at the First Lady. Trump replied: “You could handle it no question.”

Former Royal Marine Jack Smith, 94, a landing craft coxswain who was part of the first wave during D-day, enjoyed a chat with the Queen. “It means an awful lot to be here, the day respects everybody who took part in D-day,” he said. “A lot of people did a lot of good work that day, it respects their memory and the lads that didn’t come back.”

Facebook Twitter Pinterest People wave union flags on Southsea Common. Photograph: Dylan Martinez/Reuters

Trump wished happy birthday to Joan “Jonni” Berfield, a Wren who worked as a coder and will be celebrating her 95th birthday on 7 June. She said: “I think I will wake up and find it’s all a dream. It’s been a fantastic day, I’m just overwhelmed by everything.”

The event was vast. The Ministry of Defence said more than 4,000 personnel were involved in the commemorations, one of the biggest mobilisations of the UK’s armed forces in recent years.

Quick guide What happened on D-day? Show Hide What was D-day? D-day was an invasion of France by allied forces. It was codenamed Operation Neptune, and it aimed to push Nazi Germany out of occupied France. Five beaches in Normandy, codenamed Omaha, Utah, Juno, Sword and Gold, were the main targets for landing a large number of troops by sea. At 10pm on 5 June 1944, troops began departing from British shores to head across the Channel. Five assault groups set sail under darkness in an armada of about 7,000 vessels. Just after midnight on 6 June, aerial bombardment of enemy positions on the Normandy coast began. Special operations troops were also parachuted into France. US troops landed on Omaha and Utah beaches at about 6:30am. About an hour later Canadian forces landed at Juno, and British troops landed at Gold and Sword. Soldiers had to get off their boats, wade through the water, and seize control of the beach, all the while under heavy and sustained fire from German defensive positions. How was the plan kept secret? Despite involving a large number of troops, keeping D-day secret was vital to the success of the operation. A disinformation campaign had led the Germans to believe that Operation Fortitude was the main plan for the allies to invade the continent, via a two-pronged attack involving Norway and Calais. Even once the D-day landings had begun, German commanders were convinced they were just a diversionary tactic before the real invasion. Why is it called D-day? The D in D-day actually has no particular significance to Operation Neptune. It was common practice in the military to make plans that used the term, where the D stands for the day when operations commenced. Military planners also set H-hour, the time at which a plan was to begin. What happened next? By the end of the day, the allies had disembarked more than 135,000 men and 10,000 vehicles on to the beaches, and established bridgeheads of varying depths along the Normandy coastline. This came at the cost of 4,400 allied troops being killed, with thousands more injured or missing. There were also heavy casualties among German troops and French civilians. By 19 August, the allied forces had pushed down far enough to begin the battle to liberate Paris. German troops surrendered the French capital on 25 August 1944, two and a half months after D-day. Martin Belam

Miles of fencing, roadblocks and checkpoints were in place in Portsmouth, one of the major embarkation points on D-day, and residents of nearby flats were told not to aim long-lens cameras at Southsea Common or fly drones over the site. The day was alive with the clatter of helicopters and the roar of police outriders bringing dignitaries in and out.

At the commemoration event on the common, the Queen said the fate of the world had depended on the success of the operation. “The heroism, courage and sacrifice of those who lost their lives will never be forgotten,” she said. “It is with humility and pleasure on behalf of the entire country, indeed the whole free world, that I say to you all – thank you.”

Facebook Twitter Pinterest Donald Trump and the leaders of 15 other countries signed a proclamation to mark the anniversary. Photograph: Jeff J Mitchell/Getty Images

One of the most emotional moments came when Theresa May read a letter from Capt Norman Skinner of the Royal Army Service Corps, written to his wife, Gladys, on 3 June 1944. The letter was still in his pocket when he landed on Sword Beach on 6 June. Skinner was killed the day after, leaving his wife and two young daughters.

The letter read: “Although I would give anything to be back with you, I have not yet had any wish at all to back down from the job we have to do.”

The French president, Emmanuel Macron, thanked the veterans on behalf of his nation before reading another final letter, that of Henri Fertet, a resistance fighter executed aged 16. “The soldiers are coming to get me. I must hurry. My handwriting may look wobbly, but it is just because I am using a small pencil. I am not afraid of death, my conscience is completely clear … A thousand kisses. Long live France,” he wrote.

There had been grumbles from some locals who felt excluded because of the huge security operation, but there was a festival atmosphere in the public viewing area where visitors watched the ceremony on giant screens.

People brought deckchairs and picnics, and there were burger stands, beer tents and stalls selling everything from souvenir mugs to fridge magnets and tea towels.

Sally Pattenden, 42, from Southsea, said the day made her proud to be British and that she didn’t mind the minor inconveniences caused by the security operation.

“We have had lots of warnings. We couldn’t park anywhere for a while, but I think you get into the spirit of it. It is about the veterans. If you can’t give up your parking space for someone who gave their life, what can you do?”

Facebook Twitter Pinterest The MV Boudicca with D-day veterans onboard arrives in Poole, Dorset. Photograph: Andrew Matthews/PA

Politics occasionally reared its head. Sandra Tonge, who was with her husband Anthony, said: “It’s a bit of a cliche but we really all could be speaking German now for all we know if it wasn’t for the men we were remembering today.

“You come away from something like this with a different feeling. I felt that a bit more enthusiastic about Brexit for example.”

Before the Southsea Common event, the 16 nations involved in the commemorations agreed a proclamation to mark the anniversary. The statement recognises the sacrifice of those who took part in the second world war and salutes the surviving D-day veterans. The 16 countries undertake to work together to find common ground and recommit to the shared values of democracy, tolerance and the rule of law.

After the reception with veterans, the world leaders present met to discuss Nato and security. They were then whisked away by helicopter and motor cavalcade while many of the veterans took to the water on board a cruise ship to be ferried across to France accompanied by a flotilla of naval vessels.

For them, the D-day commemorations will continue in Normandy on Thursday.