Queen Elizabeth II and Prince Philip
Prince Philip and Queen Elizabeth II enjoyed separate horse riding. Pictured: Queen Elizabeth II and Princ Philip arrive in the Royal Carriage on the third day of Royal Ascot 2005, Ladie's Day, at York Racecourse on June 16, 2005 in York, England. Getty Images/Chris Jackson

Queen Elizabeth II and Prince Philip enjoyed horse riding separately.

The Duke of Edinburgh, 97, and the monarch, 92, are fit and healthy for their age. The royal couple show no signs of slowing down despite rumors suggesting that Prince Charles will be king when the Queen turns 95.

On Monday, Queen Elizabeth II and Prince Philip stepped out and enjoyed horse riding in the grounds of Windsor Castle. Daily Star shared photos of the two royals on the back of their ponies. Her Majesty was riding her beloved black Felly pony, Carltonlima Emma. The pony sported a red poppy to mark the start of Remembrance week.

Queen Elizabeth II was seen riding her horse just hours after Prince Philip was spotted venturing out. Prince Philip went carriage riding with two black horses in the fields. He was joined by two stablewomen who sat behind him.

Prince Philip wore gloves, a tweed hat and blanket for his ride. On the other hand, Queen Elizabeth II sported a headscarf and navy coat.

Prince Philip and Queen Elizabeth II's horse riding happened just days after it was reported that Prince Charles is taking over the throne in a few years. According to Robert Jobson in his book "Charles at 70: Thoughts, Hopes and Dreams," the Prince of Wales is the prince regent.

"In truth, with the Queen now well into her tenth decade, senior officials within the Royal Household confirm that Prince Charles is effectively already our 'Prince Regent', a king in all but name," he said.

"Some close to the monarch say that, if she reaches the age of 95, she will make a monumental decision and choose to officially allow Charles to take over the stewardship of her reign," Jobson added. "She will, they say, officially transfer all executive powers to him as Prince Regent until her death, when he will become king. This would enable her to fudge the issue of her not fulfilling her Coronation Oath to God and her people to serve as queen regnant until her death."

However, the Queen and Prince Philip reportedly doubt Prince Charles's suitability as the next king. In fact, they considered their son as a "loose cannon."

Meanwhile, Tom Bower said in his book "The Power, Passion and Defiance of Prince Charles" that the two senior royals wanted to live longer. In this way, they can keep Prince Charles from the throne and "have little opportunity to damage the monarchy."

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