Protesters have denounced Donald Trump as “frightening and dangerous” and claimed his state visit is “an invitation for his ideology to be imported” to the UK, during a dramatic first day of the US president's second state visit to the country.

During a state banquet at Buckingham Palace, Queen Elizabeth II greeted the president, and reminded those in attendance of the "close and longstanding friendship" between their two countries — and appeared to rebuke Mr Trump's so-called America-first ideology that has threatened once close alliances and shaken the international community.

"I am so glad that we have another opportunity to demonstrate the immense importance that both our countries attach to our relationship," the Queen said.

The itinerary for Mr Trump going forward includes meetings with business leaders, a tour of historic British buildings, and trips to Portsmouth and Normandy — with the latter coming on the 75th anniversary of D-Day.

The Queen, during her remarks, used that historic moment in the Second World War to reinforce the importance of the US-UK relationship.

Every outfit Melania Trump has worn for the UK state visit Show all 15 1 /15 Every outfit Melania Trump has worn for the UK state visit Every outfit Melania Trump has worn for the UK state visit Pre-flight Melania wears a calf-skimming shirt dress by Gucci before departing the White House in Washington DC. AFP/Getty Images Every outfit Melania Trump has worn for the UK state visit Pre-flight The cream, orange and green gown was covered in prints depicting London landmarks including the Tower of London and Big Ben. Getty Images Every outfit Melania Trump has worn for the UK state visit Day 1 Melania arrived at London's Stansted airport wearing a navy-blue skirt suit paired with a printed pussy-bow blouse by British heritage brand Burberry. REUTERS Every outfit Melania Trump has worn for the UK state visit Day 1 Melania accessorised her post-flight look with a pair of oversized sunglasses. EPA Every outfit Melania Trump has worn for the UK state visit Day 1 Melania arrived at Buckingham Palace later that day to meet the Queen at Buckingham Palace. Here she is pictured standing alongside HRH and her husband during a welcome ceremony. She wore a fitted white dress by Italian label Dolce and Gabbana. AFP/Getty Images Every outfit Melania Trump has worn for the UK state visit Day 1 Both the Duchess and Melania struggled to hold onto their hats during the ceremony. Melania's opted for a large wide-brimmed hat by American fashion designer, Hervé Pierre. The Duchess wore a cream by Irish milliner Philip Treacy. REUTERS Every outfit Melania Trump has worn for the UK state visit Day 1 At the Palace, the Trumps also met with Prince Charles and the Duchess of Cornwall, who was wearing a light-coloured ensemble by Anna Valentine. REUTERS Every outfit Melania Trump has worn for the UK state visit Day 1 Melania's hat matched the navy trim of her dress. REUTERS Every outfit Melania Trump has worn for the UK state visit Day 1 For the State Banquet at Buckingham Palace that evening, Melania made a sartorial statement in custom Dior haute couture. The ivory-coloured sleeveless gown boasted a flame-shaped neckline. The first lady accessorised the look with matching ivory gloves and diamond earrings. REUTERS Every outfit Melania Trump has worn for the UK state visit Day 2 For the presidential meeting between Theresa May and her husband Philip May, Melania wore a belted beige trench dress by CELINE. AFP/Getty Images Every outfit Melania Trump has worn for the UK state visit Day 2 Melania also wore stiletto black heels and carried a crocodile Birkin bag by Hermès. AFP/Getty Images Every outfit Melania Trump has worn for the UK state visit Day 2 On Tuesday evening, the US president and first lady hosted a dinner at Winfield House, the residence of the US ambassador. Melania wore a £5,000 floor-length red Givenchy gown for the occasion, complete with a cape design. PA Every outfit Melania Trump has worn for the UK state visit Day 2 The bold Givenchy dress featured a red sequinned v-shaped neckline. Getty Images Every outfit Melania Trump has worn for the UK state visit Day 3 On the third day of the UK state visit, Melania and Donald Trump attended a ceremony in Portsmouth in honour of the 75th anniversary of the D-Day landings. The first lady of the US dressed in an all-white ensemble for the occasion, wearing an ivory coat by New York-based brand The Row and accessorising with a wide-brim fascinator by Philip Treacy. AFP/Getty Images Every outfit Melania Trump has worn for the UK state visit Day 3 The US first lady completed her look with a pair of nude Dior heels. REUTERS

"On that day — and on many occasions since — the armed forces of both our countries fought side-by-side to defend our cherished values of liberty and democracy," she said.

"As we face the new challenges of the 21st Century, the anniversary of D-Day reminds us of all that our counties have achieved together," she continued, addressing the kinds of international coooperation in the post war years that Mr Trump appears to have disregarded as president. "After the shared sacrifices of the Second World War, Britain and the United States worked with other allies to build an assembly of international institutions to ensure that the horrors of conflict would never be repeated."

But, nearby in London, protesters denounced the president who had lashed out at mayor Sadiq Khaan as his trip loomed.

“It’s one thing to tolerate it, it is something else to promote it,” 46-year-old Hada Moreno told The Independent outside Buckingham Palace of Mr Trump's ideological stance.

But the US president’s backers were also present, calling him “a hero”. One said: “After Brexit we will need him for trade as well as security.” It came after Mr Trump lashed out at London’s mayor on Twitter, branding him “terrible” and a “stone-cold loser”.

Mr Trump and his wife Melania dined with the Queen at Buckingham Palace. The pair were met by Prince Charles and the Duchess of Cornwall, and will also take a tour of Westminster Abbey. Observers were curious as to how the Prince of Wales, a keen environmentalist, would get along with the fossil fuel-loving president.