Zara Tindall has long enjoyed a close friendship with Prince William as rumours swirl that she could take on more royal duties

A royal author has claimed that Zara Tindall is like the sister Prince William never had.

As well as being close allies, Zara and husband Mike Tindall are also both reportedly very close with Waleses, with Zara acting as godmother to the couple’s children. Speaking to Hello! magazine, author Ingrid Seward said: “Zara is the sister William never had. They’ve always had terrific fun together and they’ve always supported each other.”

Mike has also revealed in the past some of what has happened when the two couples have been on double dates. Speaking on The Good, The Bad & The Rugby podcast Mike revealed that Princess Kate was “uber competitive” at beer pong and called William “One Pint Willy” claiming the heir to the throne didn’t drink much.

Away from podcasts and double dates, there has been speculation that Zara could step up into more active royal duties as Princess Anne recovers from a concussion and Princess Kate and King Charles recover from their cancer diagnoses.

However, a friend says this is far from becoming a reality.

They said: “She can support her family and be invited to family occasions and other events, but also continue to live her life and do what she wants. The two things can co-exist. Why would she want to change that?”

The friend’s comments come after a source told the Express that Zara would not be able to join the Royal Family at Balmoral Castle because she had decided to enter the Wellington International Horse Trials.

The source said: “Charles really wants Zara and the family to join him on the last Sunday in August for the bank holiday service, but understands that her horse competitions are extremely important to her.

“Charles is hoping that they…will be able to come up the week earlier to muck in with the rest of the family so that everyone can enjoy the picnics and walks planned on the estate.

“Mia, Lena and Lucas get on amazingly well with George, Charlotte and Louis. There will be lots of children there this year so they are planning a mixture of adult and junior events to keep everyone entertained.”

The Wellington International Horse Trials are due to take place in Hampshire between August 24 and August 26.