Mother-in-laws can sometimes be tricky to deal with - and worrying about how they may react might be amplified if they're a princess.

"M'am, not Mum!" said the retired rugby star, who is married to the Princess Royal's daughter, Zara Mike Tindall knows just what to call his royal mother-in-law, Princess Anne. On Nov. 4, the retired rugby star made the revelation while appearing on Good Morning Britain to discuss his new book,

Mike Tindall has highlighted the special roles that Princess Kate, Prince William and Princess Anne hold in the world of rugby. The former England international rugby player who is married to Princess Anne's daughter Zara Tindall has a strong bond with the senior members of the Royal Family.

Mike Tindall has given a unique insight into his close bond with Princess Anne - including what he calls his mother-in-law behind closed doors. The former rugby professional married Zara Tindall - who is Princess Anne 's only daughter - back in 2011. The pair, who met in 2003, now share three children - Mia, 10, Lena, six, and three-year-old Lucas.