Quiet celebrations as Anne turns 60
The Princess Royal is expected to mark her 60th birthday in a low-key manner, spending it privately with family.
A Buckingham Palace spokesman said no public engagements were planned for the day.
Her two children, Zara and Peter Phillips, paid warm tribute to her role as a mother in the BBC programme The Princess Royal at 60: an Inside Sport Special, which aired earlier this week to mark the milestone.
In a revealing exchange, Zara said: "I would like to be as good a mother as she has been to us."
Peter added: "Her advice generally about life has been invaluable. Whenever we may have got slightly above our station she'd be the first one to bring us back down to earth fairly hard."
Anne, a keen equestrian, represented Great Britain at the 1976 Montreal games as a member of the British three-day event team and was elected to the International Olympic Committee (IOC) in 1988. She was voted the BBC's Sports Personality of 1971.
Anne married her second husband, naval officer Commander Timothy Laurence, in a low key ceremony in 1992, after her first marriage to fellow equestrian Lieutenant (later Captain) Mark Phillips ended in divorce after 19 years.
The Queen's second eldest child and only daughter is a supporter of many charities and last year she carried out almost 600 public engagements.
She has been president of the Save the Children fund since 1970.
Asked if she would ever slow down on her commitments, Anne said: "Look around at the members of my family who are considerably older than me and tell me whether they have set an example which suggests I might - unlikely."