The actresses linked to Prince Philip during his early days with the Queen

As Prince Harry's relationship with Meghan Markle was getting serious, he was allegedly advised to proceed with caution with the American actress.

His grandfather, Prince Philip, is rumoured to have told Harry: "One steps out with actresses, one doesn’t marry them" reports The Sun.

Perhaps Philip's own rumoured experience with women in showbiz prompted him to give Harry the pearls of wisdom.

Viewers of The Crown will believe the Queen's husband, Prince Philip, had a wandering eye and may have even been unfaithful to his wife.

The hit television series explores the Duke of Edinburgh's rumoured indiscretions during his early years of marriage to Queen Elizabeth. One of those alleged dalliances, featured in the show, was with Russian ballerina Galina Ulanova. While there is no proof as to whether anything happened between Ulanova and the Duke, she wasn’t the first woman in the showbiz industry linked to Philip in real life.

Rumours of extra-marital affairs plagued the royal relationship, especially during the early years.

Prince Philip was said to have had a fling with dancer and singer Patricia Kirkwood after they met in 1948 in her dressing room at the Hippodrome Theatre, where she was starring in Starlight Roof. Afterwards, it's believed they dined alone before dancing the night away at a London nightclub. The then-Princess Elizabeth was eight months pregnant with Prince Charles at the time.

Philip and Kirkwood's alleged affair carried on for some time, and a series of letters were exchanged. Those letters are now in the possession of royal biographer and historian Michael Thornton who is under instruction, in accordance with Kirkwood’s will, "to show them to no one except the Duke’s official biographer, when one is appointed after his death". Thornton told The Telegraph that the correspondences were "written in terms of concerned friendship by two people caught up in a media maelstrom".

Kirkwood consistently denied an affair with the Duke, telling a journalist "A lady is not normally expected to defend her honour… It is the gentleman who should do that. I would have had a happier and easier life if Prince Philip, instead of coming uninvited to my dressing room, had gone home to his pregnant wife on the night in question".

Another woman linked to Prince Philip was French-born Greek actress Hélène Cordet, who was childhood friends with the Duke.

She was eventually forced to deny allegations he was the biological father of her two sons, born in 1943 and 1945. Adding fuel to the fire was the fact Hélène had recently separated from her first husband.

Prince Philip was also rumoured to have had a relationship with Oscar-nominated British-Asian actress Merle Oberon, who was nicknamed 'Queenie' and was 10 years his junior.

Historian Michael Thornton claimed Oberon kept a signed photograph of Prince Philip in a frame.

But biographer Sarah Bradford believed Philip preferred women who weren't actresses, writing in Queen Elizabeth II: Her Life in Our Times that "he's never been one for chasing actresses. His interest is quite different. The women he goes for are always younger than him, usually beautiful, and highly aristocratic".

The Duke was linked with Sacha, the Duchess of Abercorn who was 25 years his junior. She told royal author Gyles Brandreth, who was a friend of Philip's, that she had a relationship with the royal.

In Brandreth's book, Philip & Elizabeth: Portrait of a Marriage, the Duchess said: "Our friendship was very close [but] I did not go to bed with him.

"It's complicated and at the same time it's quite simple. He needs a playmate and someone to share his intellectual pursuits."