Presidential visits are enormous affairs and the security operation which will accompany Trump and his family is formidable. Air Force One - the president's jet - is a heavily-defended flying White House. The presidential motorcade, which includes two identical limousines and more than 20 other security and communications vehicles, is transported ahead of the visit by United States Air Force transport aircraft. On the ground, the president travels in Cadillac One - an armoured, high-powered enhanced limousine known as "The Beast". And there will have to be an enhanced police presence, taken from the ranks of the host country's own forces. For the last state visit in June 2019, more than 6,300 UK police officers were deployed at a cost to London's Metropolitan Police of £3.4m. A previous four-day working visit in 2018 cost more than £14.2m. Trump's 2018 trip to Scotland is thought to have seen more than 5,000 officers deployed, with the UK Treasury chipping in about £5m to help with the costs. So there are already concerns about how much this "private" trip will cost Scotland, especially against a backdrop of police complaints about spending on the force. The Scottish Police Federation (SPF), which represents rank-and-file officers, has raised concerns about what the Trump visit will mean for its members. Police Scotland confirmed it was preparing for a presidential visit earlier this month. The Scottish government said it had been working with the national force to put plans in place, with thousands of officers likely to be deployed as part of the security operation.