It was Mr Kidston, on behalf of a client, who made the winning bid. Its new owner has chosen to remain anonymous.
“If you had asked classic-car experts and top collectors over the past half a century to name the most desirable car in the world, there’s a good chance that they would have come up with the same model: the Mercedes-Benz 300 SLR.”
The auction took place on May 5, with bidders hand-picked by the German carmaker.
The 1955 car was put up for auction by the Bavarian marque despite it previously being adamant that it would never be sold.
Mr Kidston said that refusal to sell had given the car part of its appeal.
“It’s a combination of exotic engineering, all-conquering racing history, the power of the three-pointed star on its nose and the fact that one had never, ever been sold. Many collectors had tried, all had failed.
“That was what the entire motoring world thought, but times change, and if you don’t ask, you’ll never know.”
Speaking about his personal lobbying efforts, he said: “A long-standing relationship with the Mercedes-Benz Museum helped, but even after 18 months of patient lobbying, we didn’t know if or how they would consider letting the 300 SLR out of captivity until just before it happened.
“For everyone involved, and especially the new owner whom we represented, this was a once-in-a-lifetime chance to buy the Mona Lisa of cars.”