For Queen Elizabeth, Britain's unflappable monarch, the arrival of US President Donald Trump, his family and his armoured entourage on Monday means a full day of ceremony topped by a magnificent banquet at Buckingham Palace.

Yet beneath the pomp and ceremony, there are differences aplenty.

There will be a formal tea on Monday afternoon hosted by Prince Charles and his wife Camilla for Trump and first lady Melania Trump, bringing together a future king who has warned about the perils of climate change for years with a president who is actively dismantling US policies designed to slow global warming.

On the political front, Trump meets on Tuesday with British Prime Minister Theresa May only days before she steps down on Friday as Conservative Party leader, kicking off a race to succeed her as prime minister.

Trump professes friendship for May, but he has been harshly critical of her handling of Britain's tortured Brexit negotiations with the European Union.

He has also buddied up to former Foreign Secretary Boris Johnson, a May critic who hopes to follow her into power, and Brexit Party leader Nigel Farage, who accuses May of incompetence and betrayal.

Trump ramped up his interference in British politics by telling the Sunday Times that Britain should "walk away" from talks and refuse to pay a STG39 billion ($A71 billion) divorce bill if it doesn't get better terms from the EU. He also said Farage should be given a role in the Brexit negotiations.

The long-delayed state visit was timed to coincide with solemn ceremonies in Britain on Wednesday and in France on Thursday marking the 75th anniversary of the D-Day invasion.

Still, the very topic of a Trump visit to Britain has been deeply divisive since May extended the invitation on behalf of the Queen in an Oval Office visit in the first week of Trump's administration.

The move prompted street protests in Britain, an online petition signed by more than 1 million opposed to the idea, and a debate in Parliament over whether Trump deserved the highest honour that Britain can bestow on a foreign leader.

His brief working visit to Britain last summer generated huge protests in the streets of London even as Trump stayed - literally - above the fray by relying on a helicopter to get around.

That July visit also marked the debut of the "Trump baby balloon" - an inflatable piece of conceptual art that depicts the president as a baby wearing nappies.

Some serious topics are to be discussed, including the Trump administration's determined effort to prevent Britain from relying on Chinese tech giant Huawei to build parts of its 5G communications network.

National Security Adviser John Bolton told reporters before Trump's arrival that allowing this could give China's government a "back door" into western telecommunications systems.

Some of the traditional trappings of an official state visit are likely being scaled back.

Typically one of the highlights is a carriage ride procession that brings the visiting dignitary to the Buckingham Palace grounds escorted by a large number of mounted soldiers from the Household Cavalry as gun salutes are made from nearby Green Park and the Tower of London. Officials have not said whether that will happen this time, possibly due to security concerns that a slow-moving procession of horse-drawn carriages could prove an irresistible target for protesters.

The president and first lady also are not going to stay at Buckingham Palace, where state visitors usually lodge, apparently because of renovations underway at the 775-room residence. They are expected to stay at Winfield House, the spacious home of the US ambassador.

The Trumps and their grown children are expected to meet Prince William, a future king, and his wife Kate, the Duchess of Cambridge. Prince Harry is also set to meet the Trumps, but his wife Meghan, the Duchess of Sussex, is expected to stay at home with their newborn son Archie.

Meghan, a former actress who has campaigned for women's rights around the world, is a fellow American who was critical of Trump and backed his political rival Hillary Clinton before she married into the royal family.

Australian Associated Press