Princess Beatrice can act as a stand-in for King Charles.
The 34-year-old princess - who works as vice-president of strategy and partnerships at software company Afiniti - has moved up the line of succession following the death of Queen Elizabeth last week and although she isn't officially a working royal, she will now be one of the monarch's Counsellors of State, meaning she can carry out his official duties if he falls ill or is abroad, The Times newspaper reports.
The law states that those allowed to take on the work for Charles include his spouse, Queen Consort Camilla, and the next four people over the age of 21 in the line of succession, meaning that as ninth in line to the throne, Beatrice joins her cousins Princes William and Harry and her father Prince Andrew in being able to undertake the duties.
William's children, Princes George and Louis, nine and four, and seven-year-old Princess Charlotte, and Harry's kids, Archie, three, and Lili, 15 months, all come above Beatrice in the line of succession but are too young for the roles.
With Harry having stepped back from royal duties after moving to the US with wife Meghan two years ago and Andrew stripped of his royal titles and patronages in the wake of his civil sex assault case scandal, Beatrice is likely to be the next person after Camilla and William.
It is rare for Counsellors of State to need to step up, but in May this year, William and Charles stood in for the queen at the state opening of Parliament because of her health issues.
The position was created in 1936 when King George VI became head of state and was designed to cover short term absences and avoid unnecessary regencies.
However, some duties cannot be delegated to the Counsellors of State - who must be aged over 21 and British citizens living in the UK - including appointing the Prime Minister, the creation of peers and Commonwealth matters.
They also cannot carry out the Dissolving of Parliament unless explicitly instructed to do so by the monarch.
Heir to the thrones can be named Counsellors of State from the age of 18.