The Princess Royal will travel to South Africa for a two-day trip without husband Vice Admiral Sir Tim Laurence, who has suffered a suspected torn ligament.
Anne begins with a visit to Cape Town but is travelling by herself after Sir Tim was injured while working on her Gatcombe estate, it is understood.
The former naval officer needs treatment in the UK and is unable to fly with the princess, who will travel by a commercial flight and start the trip with a project close to her heart – horses supporting the disabled.
Anne will watch riders being put through their paces at the Cape Town-based organisation South African Riding for the Disabled Association.
Sir Tim Laurence (Jonathan Brady/PA)
It is similar to the UK charity Riding for the Disabled, which the princess supports as president, with both using horse riding to help children and adults with physical disabilities to improve their wellbeing.
Later at the British High Commission, Anne will view an exhibition by former England cricketer Nick Compton, grandson of renowned batsman Denis Compton.
During the two-day visit the princess will commemorate the sacrifices of black South Africans and other races who played a vital role as military labourers during the First World War.
She is president of the Commonwealth War Graves Commission and will unveil the organisation’s Cape Town Labour Corps Memorial, which honours more than 1,700 South Africans who carried out non-combat jobs and died with no known grave or commemoration.
She will also visit the Desmond and Leah Tutu Legacy Foundation, which keeps alive the memory and achievements of the former archbishop of Cape Town who was awarded the Nobel Prize for Peace in 1984 for his opposition to apartheid in South Africa.
Anne, who last visited South Africa in 2012 to commemorate Queen Elizabeth II’s Diamond Jubilee, will also visit the Royal Cape Yacht Club and the South African Astronomical Observatory.