Donald Trump's four-day visit to the UK in July cost police almost £18m, the National Police Chiefs' Council (NPCC) has revealed.
Thousands of officers were deployed to cover the presidential visit in what was the largest mobilisation since the London riots of 2011, with Mr Trump travelling to four different force areas over the course of his stay.
Several protests also took place across the country, which required their own policing.
NPCC chair Sara Thornton said: "Nearly every force supported the operation with nearly 10,000 officers deployed from all over the country, performing over 26,000 shifts.
"The full cost of the operation is still being worked out but an early estimate is nearly £18m."
That figure puts the security costs of the trip well above those incurred by either of the royal weddings this year, which required police in Windsor to ask the Home Office for extra money.
Between £2m and £4m is thought to have been spent on security when the Duke and Duchess of Sussex married, and another hefty bill will be wracked up when Princess Eugenie marries her fiance Jack Brooksbank on Friday.
Ms Thornton said police were in especially "high demand" at the time of the visit of Mr Trump, as it coincided with increased calls linked to the World Cup, hot weather, and numerous events and festivals.
"These demands affected local policing to differing degrees across the country with the host forces most impacted," the senior officer added.
"The majority of forces had to cancel officers' rest days and extend the length of their shifts.
"Despite the challenges, the hard work of officers and staff made sure that the public were kept safe throughout."
Mr Trump was kept busy during his first stay in the UK as president – he held talks with Prime Minister Theresa May and also enjoyed tea with the Queen at Windsor Castle.
He managed to avoid most of the thousands of protesters opposed to his visit, with the demonstrations headlined by the appearance of a huge nappy-clad orange balloon dubbed "Trump baby".
Mayor of London Sadiq Khan gave the all-clear for the blimp to fly after thousands signed a petition and a crowdfunding campaign raised more than £16,000 to get the six-metre inflatable off the ground.
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The only protesters who managed to secure an acknowledgement from the president were those who turned up at his golf resort in Scotland on the final day of his visit.
He was still able to enjoy a few rounds at Turnberry before boarding his plane to Helsinki for what would prove to be a controversial summit with Vladimir Putin.