Mike Tindall has shared a heartfelt note for his wife Zara to mark her 45th birthday today amid Prince William’s royal plans for his cousin.

According to media reports, the Prince of Wales has big plans when he becomes King to promote Zara, one of his most trusted family members to a key royal role.

A royal insider recently told the New Idea, “After Harry and Andrew, William understands completely the importance of having trust — and Zara, along with her husband Mike, are definitely in that category.”

“It’s no secret William has plans for Zara when he takes over and already there’s been talk of her taking on patronage of the Royal Stud at Sandringham, plus some oversight of royal racing interests at events like Ascot and Cheltenham.

“It makes complete sense as William’s nowhere near as enthusiastic about equestrian pursuits like his grandmother was, so delegating this entirely to Zara is a brilliant plan.

"This new role plays into Zara’s strengths as an Olympic silver-medal equestrian.”

Amid Prince William’s plans, Mike took to social media and shared a sweet photo with Zara to celebrate her special day.

Sharing the photo on Instagram, Mike said: “I can’t believe she’s letting me play golf on her birthday. What a legend!” followed by a heart emoticon.