Mike Tindall's dad is a "shell of what he once was" because of Parkinson's Disease.

The former rugby player - who is married to Princess Anne's daughter Zara Tindall - admitted his father Philip is "not doing great" at the moment amid his battle with the degenerative condition, which he was diagnosed with in 2003.

He told Britain's HELLO! magazine: "My dad is not doing great at the moment. Parkinson's is brutal and there is no let up from how it attacks the body and changes people.

"After 23 (plus) years of the disease, it has quite honestly left him a shell of what he once was, which is why I don't want anyone else to see a parent or loved one suffer and have their quality of life decline so massively."

Witnessing how the condition has impacted Philip has driven Mike to help fundraise to find a cure for Parkinson's.

He said: "It gives me so much motivation to help push for a cure and work with Cure Parkinson's on their research, trials and really important work to try and end this disease."

To raise funds for Cure Parkinson's and sporting-injury charity The Matt Hampson Foundation, Mike held his annual charity tournament, the ISPS Handa Celebrity Golf Classic at The Belfry on 15 May - which also happened to be his wife's birthday.

But Mike insisted the Olympian was only too happy to celebrate turning 45 at the star-studded event.

He said: "I can't believe she's letting me play golf on her birthday What a legend!

"Zara loves the golf day.

"It's such a great occasion with a lot of friends and people who just want to have a good time. She helps with their golf swing by making sure they have plenty to drink and is on hand with mulligans [permissions to disregard a bad shot, in exchange for a charitable gift] to help ease the pain of a bad round. All of which makes a huge amount of money for charity so it's a win-win.

"She gets a load of mates in one place, and a big party on her birthday!"

The couple have three children, Mia, 12, Lena, seven, and five-year-old Lucas, but they're not pushing them into following in their footsteps to pursue sporting careers, as they want them to focus on having fun while being active.

Mike said: "My main focus is that they enjoy sport and it's an important part of their life - whatever form or level that takes is up to them, but I want them to have fun and be part of something where you have wins and losses and work out how to get through it with teammates who you can have a laugh with."