Knowing what to give someone as a wedding present is never an easy undertaking, but it's even harder when the couple in question are royalty. When the Prince and Princess of Wales got married back in 2011, however, The King had a very special and unexpected surprise in mind for them to mark the special occasion.

One of King Charles' most prized possessions was gifted to him for his 21st birthday by his own parents - a car. 'It’s an Aston Martin DB6 MkII Volante in Seychelles Blue,' says former royal butler Grant Harrold. 'He’s very, very protective of that car. He never let anyone else drive it. It was a big issue as I remember both William and Harry wanting to drive it, but he wouldn’t let them.'

london, england april 29: trh prince william, duke of cambridge and catherine, duchess of cambridge smile following their marriage at westminster abbey on april 29, 2011 in london, england. the marriage of the second in line to the british throne was led by the archbishop of canterbury and was attended by 1900 guests, including foreign royal family members and heads of state. thousands of well wishers from around the world have also flocked to london to witness the spectacle and pageantry of the royal wedding. (photo by chris jackson/getty images)
Chris Jackson

While Prince William may have spent his teens and twenties dreaming of driving his dad's prized vehicle to no avail, The King decided to finally grant him his wish for one special occasion. 'He let William and Kate borrow it on their wedding day, and that was a big deal.' Given the car had been gifted to The King by his parents, it was an especially poignant touch to lend it to his son on his big day.

london, england april 29: prince william, duke of cambridge and catherine, duchess of cambridge drive from buckingham palace in a decorated sports car on april 29, 2011 in london, england. the marriage of the second in line to the british throne was led by the archbishop of canterbury and was attended by 1900 guests, including foreign royal family members and heads of state. thousands of well wishers from around the world have also flocked to london to witness the spectacle and pageantry of the royal wedding. (photo by julian finney/getty images)
Julian Finney
The Prince and Princess of Wales on their wedding day.
london, england april 29: prince william, duke of cambridge and catherine, duchess of cambridge drive from buckingham palace to clarence house in a decorated vintage aston martin sports car on april 29, 2011 in london, england. the marriage of the second in line to the british throne was led by the archbishop of canterbury and was attended by 1900 guests, including foreign royal family members and heads of state. thousands of well wishers from around the world have also flocked to london to witness the spectacle and pageantry of the royal wedding (photo by jeff j mitchell/getty images)
JEFF J MITCHELL
topshot britains prince william drives an aston martin as he leaves the buckingham palace with his wife kate, duchess of cambridge, after their wedding service, on april 29, 2011, in london. afp photo / pierre philippe marcou (photo by pierre philippe marcou / afp) (photo by pierre philippe marcou/afp via getty images)
PIERRE-PHILIPPE MARCOU

Grant says The King lets almost nobody else ever drive his car, but there was 'one occasion when one of the chefs had to drive it back from the airport and it was a massive honour, but it caused a big who-ha. I remember him giving him strict instructions about how slow to drive it and what to do.'

criencester, united kingdom june 17: (embargoed for publication in uk newspapers until 24 hours after create date and time) prince charles, prince of wales accompanied by camilla, duchess of cornwall arrives, driving his 1969 aston martin db6 volante, to play in the burberry cup polo match at cirencester park polo club on june 17, 2005 in cirencester, england. (photo by max mumby/indigo/getty images)
Max Mumby/Indigo
The King’s car is one of his most prized possessions.

The King has been pictured on many occasions out for a drive in his Aston Martin, sometimes with Queen Camilla in the passenger seat. 'He used to drive it around Tetbury with the roof down. People’s faces when he went past were just priceless,' says Grant, via Select Car Leasing. 'I remember once this woman almost pulled her husband over when she grabbed him because she was so shocked to just see him driving normally. Of course he would always give a little wave.'

barry, wales february 21: prince charles, prince of wales is seen next to his aston martin db6, during his visit to the new aston martin lagonda factory on february 21, 2020 in barry, wales. (photo by rebecca naden wpa pool/getty images)
WPA Pool
unspecified june 28: (file photo) hrh prince charles and camilla parker bowles are seen is his aston martin car on june 28, 2003 in an unspecified location. clarence house has confirmed today that charles and partner camilla parker bowles will marry, at a date expected to be circa april 6, 2005. (photo by tim graham photo library via getty images)
Pool/Tim Graham Picture Library

While the Aston Martin may look like an ordinary (if very nice!) car, The King has made some very unusual adjustments to it. 'The interesting thing about [the Aston Martin] is that [King Charles] had it modified in 2008 so it runs on wine and cheese. We couldn’t believe it when we found out, we used to joke about it a lot in the staff room.'

While the decision might seem bizarre, it was actually an eco decision by The King to move his vehicle away from petrol and diesel. 'He’s so conscious of the environment, and was long before it became mainstream. He was always looking for ways he could to protect the environment, it’s something he’s so passionate about,' says Grant.