THOMAS Markle will never meet his royal grandchild, an expert on the monarchy has claimed.

Royal writer Duncan Larcombe will make the comments in a forthcoming documentary.

In a preview for TLC's Meghan and Harry: A Royal Baby Story, Larcombe, author of Prince Harry: The Inside Story, says: "I can't think for a moment that Thomas Markle will ever be able to meet his grandson or granddaughter."

Thomas and Meghan have had a notoriously tricky relationship after it was revealed he staged photos of himself preparing for her May wedding last year.

In the faked snaps he was seen reading a book on England and being measured up for a suit.

Since then he has made numerous public appeals for his daughter to contact him.

Also appearing in the documentary is Meghan's half-sister Samantha Markle.

She says: "You can't hurt people like this and then turn around and flip the script and play victim."

Samantha has previously suggested Meghan take a "lie detector test" after contents of a letter between her father and his daughter were revealed to the press.

The letter said: “On a daily basis, you fixated and clicked on the lies they were writing about me, especially those manufactured by your other daughter, who I barely know.

"You watched me silently suffer at the hands of your vicious lies, I crumbled inside."

I can't think for a moment that Thomas Markle will ever be able to meet his grandson or granddaughter.

Samantha said: “I would challenge her to take a lie detector test anywhere on the planet with investigators that are not paid by her to skew the results.

"Quite frankly I had faith in her on and off to do the right thing by her dad but I’m sick of the bulls***.

"Nobody is trying to get close to her but she’s not going to ghost, insult and destroy this family and skip on her merry way without the truth being revealed.”

Meanwhile, celebrity journalist Ashley Pearson told the documentary: "I don't think Meghan and Kate will ever be super good friends."

There have been ongoing rumours the duchesses are not close, leading to Harry and Meghan moving out of Kensington Palace to Frogmore House.

The documentary will air on TLC next Tuesday at 8pm in the US.