Donald Trump's historic state visit to the UK began with a day of pomp and pageantry, as the US president was treated to a day of royal ceremony in Windsor.

The King, the Queen and the Prince and Princess of Wales welcomed Trump and his wife Melania to Britain to mark the beginning of the visit.

The American leader and the first lady were treated to a personal, family-centred greeting outside Victoria House, a little-known property nestled in the Royal Kitchen Gardens at Frogmore on the private Windsor estate.

William and Kate were deployed at the start of the royal charm offensive to greet the Trumps who arrived in Marine One, the call sign of the United States Marine Corps aircraft carrying the president.

The princess gave Mr Trump a broad smile as they shook hands at Windsor Castle.

The president shook hands warmly with William and patted the heir to the throne affectionately on his right arm.

The Trumps were joined by the Duke and Duchess following their arrival - with William and Mr Trump chatting in the middle of the group, while the US president held his wife Melania's hand.

William was heard to say, "This is my father," to Mr Trump as they approached the King, and Charles gestured with a small wave of his hand.

Mr Trump shook hands with the King and the pair chatted enthusiastically together, with the president also placing his hand on Charles's arm as they shook hands.

The King was earlier seen chuckling and flattening down his hair at Victoria House after the downdraft from a noisy Marine One lifting off sent gusts of wind across the walled garden to the house.

The state-of-the-art presidential helicopter, fitted with missile defence and radar jamming systems, landed on the lawn of the vast Walled Garden in the Berkshire grounds at 12.14pm on Wednesday.

The King had arrived with the Queen in the state Bentley at 12.02pm before heading inside Victoria House, where Charles could be seen standing just inside a door and watching the helicopter land.

The timings were slightly behind schedule with Mr Trump stepping out of the helicopter at 12.16pm, behind the planned time of 11.55am.

The prince and princess escorted the president and his wife a short walking distance to meet the King and Queen in front of the gable-ended Victoria House.

The unique setting, never used before at an incoming state visit in modern times, is just one of a number of flourishes being added to impress the controversial billionaire-turned politician, who sees the King as his "friend".

Camilla rallied to attend the first engagement of the key diplomatic royal duty after pulling out of the Duchess of Kent's funeral on Tuesday due to acute sinusitis.

The Queen wore a vibrant sapphire blue dress, a matching coat by Fiona Clare, a hat by Philip Treacy and a sapphire and diamond brooch.

A Beating Retreat with around 200 military musicians later performed for Mr Trump, followed by a flypast of the Red Arrows. It marked the first time they had ever been deployed for a state visit.

During the ceremony, a protest in London organised by the Stop Trump Coalition against the visit saw around 5,000 people take part, according to police.

Later, members of the royal family joined Trump for a lavish state banquet, with a guest list of 160 business moguls and politicians. Both the US president and King delivered speeches to mark the occasion.

Donald Trump's historic second UK state visit: In pictures