The long-term friendship between Prince Philip and Penny Knatchbull is to be featured in the next episodes of the Netflix fictional show portraying the lives and woes of the Royal Family. But one TV insider believes the Windsors will be far from pleased to see this association portrayed on screen.

       The insider told the Sun: "The highly personal relationship is unlikely to be welcomed as a storyline by the Queen or the rest of the Royal Family."

       Contacted by Express.co.uk, Buckingham Palace did not comment.

       Mrs Knatchbull, who bears the title of Countess Mountbatten of Burma, was born Penelope Eastwood.

       She was introduced to the late Prince Philip in the Seventies, while she was dating Norton Knatchbull.

       Mr Knatchbull is the godson of the Duke of Edinburgh and the grandson of Philip's uncle and mentor - Lord Louis Mountbatten.

       The friendship between Mrs Knatchbull and the late Duke started due to their shared interests.

       But it blossomed in 1991, when Philip supported Ms Knatchbull following the death of the Knatchbulls' daughter Leonora.

       At the time, the Duke of Edinburgh invited Ms Knatchbull to take on carriage driving - a sport he eagerly practised for decades after turning 50.

       With time, the pair became regular carriage driving companions and Ms Knatchbull was widely accepted as one of Philip's longest and most loyal friends.

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       Ms Knatchbull was described as a "keeper of secrets" by Ingrid Seward in her biography Prince Philip Revealed.

       She said: "We’ll never know how the Queen felt about it all.

       "Philip always was a flirt and the Queen used to joke about his lascivious nature.

       "If she had been hurt by rumours of supposed dalliances, she would never let on."

       As a testimony of their lasting friendship, Ms Knatchbull was one of the very few non-royal guests at Philip's funeral in April.

       However, it was stressed she was attending the socially distanced funeral on behalf of her husband, who was "unwell and unable to attend".

       The relationship between the Knatchbulls and the Windsors is strong and goes beyond the Countess and Prince Philip.

       Mr Knatchbull is believed to have taken Prince Charles under his wing while they were attending Scottish boarding school Gordonstoun.

       Years later, Charles was the Earl's best man when he tied the knot with Mrs Knatchbull a few months after the IRA killed Lord Mountbatten.

       In 2016, the Knatchbulls' daughter Alexandra got married and was walked down the aisle by Charles.

       Moreover, the Earl and Countess' son Nicholas was a year above Prince William at Eton.

       The new season of The Crown will see a new cast taking over to represent the royals during the turbulent Nineties.

       The Queen will no longer be played by Olivia Colman, replaced by Imelda Staunton.

       Tobias Menzies, who interpreted Prince Philip during seasons three and four of the show, will be replaced by Jonathan Pryce while Natascha McElhone will play Mrs Knatchbull.

       During its past four seasons, The Crown depicted royal events and relationships in a heavily fictionalised manner.

       The focus of the fourth season - Prince Charles and Diana's relationship and the heir to the throne's affair with Camilla Parker Bowles - sparked the ire of many royal watchers and experts, who feared watchers would confuse Netflix's sometimes inaccurate or embellished portrayal of the events with history.

       Many called for the streaming platform to place a health warning before every episode of The Crown to inform the viewers it is a work of fiction - an appeal rejected by Netflix.