US President Donald Trump wants to ride in the Queen's gold-plated royal carriage when he travels to London on a state visit - an insistence that has thrown British security forces into a tizzy, a media report has said.
The White House has made clear it regards the carriage procession as an essential element of the itinerary for President Trump's visit currently planned for the second week of October, The Sunday Times reported, citing officials.
But security officials have warned that the carriage journey down The Mall to Buckingham Palace will require a "monster" security operation, far greater than for any recent state visit, the paper said.
The Metropolitan Police was already facing a challenge in ensuring the safety of the controversial president as tens of thousands of people are expected to protest his visit.
The carriage "would not be able to put up much resistance in the face of a rocket propelled grenade or high-powered ammunition," the paper quoted one security source as saying.
Citing the source, the paper said that this recent demand has only served to increase complexity of the arrangement.
"The vehicle which carries the president of the United States is a spectacular vehicle. It is designed to withstand a massive attack like a low-level rocket grenade.
"If he's in that vehicle he is incredibly well protected and on top of that it can travel at enormous speed. If he is in a golden coach being dragged up the Mall by a couple of horses, the risk factor is dramatically increased," the source said.
Still, the White House regards the carriage procession as an essential element of the itinerary for Trump's state visit.
Trump's predecessor former president Barack Obama had travelled in an armoured, bullet-proof car to meet the Queen during his visit to the UK in 2011.
World leaders have been treated to the traditional Horse Guards welcoming parade - in which the Queen's carriage is drawn down The Mall to Buckingham Palace by six white horses.
Russian President Vladimir Putin and Chinese President Xi Jinping have also taken such carriage rides during state visits.