Prince Phillip's 1954 Lagonda realised £350,000 ($508,650) at H&H Classics on April 20 - a new world record for the model.
It was bought by an anonymous American buyer.
The sum is around three or four times the value of an average Langonda, indicating the value that royal provenance imparts.
The previous record was £80,000.
Philip owned the car from new up until 1961. He brought it with him on a tour of the Commonwealth in 1956-1957 and photos exist of him driving it in Melbourne.
It includes a number of extras not included on the regular model, including a radio telephone set to the Prince's personal frequency and a vanity mirror on the passenger side for the Queen.
Damian Jones, sales manager at H&H, comments: "This car is part of our history. The accompanying paperwork beggars belief.
"There is an amusing story about Prince Phillip driving Her Majesty through London in this car and being held up by a policeman on point duty directing traffic.
"When the policeman saw who was in the Lagonda he did a double take and swiftly waved them on."
The prince was actually briefly reunited with the car at a Royal Electrical and Mechanical Engineers (REME) event in 1999.
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