Trump said Queen Elizabeth was a "great, great woman... a constant symbol of these priceless traditions"

Donald Trump hailed Queen Elizabeth II as a "great, great woman" as the British monarch threw a lavish banquet for the US president on Monday to kick off his three-day state visit.

The Trump dynasty sat down to a glittering dinner with the British royal family in the Buckingham Palace ballroom as the UK rolled out the red carpet.

Both Trump and the 93-year-old sovereign praised the common bond between Britain and the United States.

But the warmth was not shared all round, with mass protests planned for Tuesday, opposition political figures boycotting the banquet and the trip starting with a spat between Trump and London Mayor Sadiq Khan.

Trump's visit is centred on the 75th anniversary of D-Day and the liberation of Europe in World War II.

"As we honour our shared victory and heritage, we affirm the common values that will unite us long into future," he said at the banquet.

"Freedom, sovereignty, self-determination, the rule of law and reverence for the rights given to us by almighty God."

He said Queen Elizabeth was a "great, great woman... a constant symbol of these priceless traditions", who embodied British "dignity, duty and patriotism".

Queen Elizabeth said Britain and the United States had built post-war international institutions for "nations working together to safeguard a hard-won peace".

The monarch said the two nations were united by their security, shared heritage, strong cultural links and strong economic ties.

"I am confident that our common values and shared interests will continue to unite us."

'Great Love All Around'

The British sovereign earlier welcomed Trump and his wife Melania with a military guard of honour on a day filled with ceremony and personal touches.

The monarch hosted a private lunch for the couple and showed them the royal art collection, ahead of the glittering banquet.

Trump seemed to be enjoying the visit, taking to Twitter during his down time.

"London part of trip is going really well. The Queen and the entire royal family have been fantastic. The relationship with the United Kingdom is very strong," he said.

"Haven't seen any protests yet, but I'm sure the fake news will be working hard to find them. Great love all around."

But the day began with controversy as, even before his plane touched down, the president lambasted Khan, who on Sunday revived their spat by comparing Trump to 20th-century fascists.

Trump, in return, called him a "stone cold loser" who had done a "terrible job" as London mayor.

Eight members of the Trump dynasty were at the state banquet, with the four eldest of Trump's five children joining 16 members of the royal family and business chiefs at the U-shaped table.

They dined on steamed fillet of halibut followed by saddle of new season Windsor lamb, strawberry sable with lemon verbena cream and fresh fruit.

Protests Planned

Trump's visit comes at a difficult time for Britain, with Theresa May due to step down as prime minister within weeks, over her handling of Brexit.

Trump weighed in on the impasse at the weekend, saying he would walk away if he could not get a deal he liked.

"Big trade deal is possible once UK gets rid of the shackles. Already starting to talk!" he tweeted Monday.

The UK-US "special relationship" was already under strain over different approaches to Iran, the use of Chinese technology in 5G networks, climate change, and Trump's personal politics.

May announced her impending resignation last month after failing to get her Brexit plan through parliament and twice delaying Britain's departure.

Trump's first official visit to Britain last year was also marked by criticism of May's Brexit strategy and large protests.

Demonstration organisers are hoping for a repeat of the protests on Tuesday during which they will once again fly a bright orange "baby Trump" balloon.

Labour's main opposition leader Jeremy Corbyn boycotted the state banquet, along with other opposition leaders and John Bercow, the speaker of parliament's lower House of Commons.

Corbyn instead made a last-minute decision to speak at Tuesday's anti-Trump demonstrations, calling them "an opportunity to stand in solidarity with those he's attacked", including Khan.

On Wednesday, May and Trump will join other world leaders in the English port of Portsmouth to commemorate 75 years since the D-Day landings, which changed the course of World War II.