The Queen has continued her official duties with a telephone call to the head of the British Army, while Prince Philip remains in hospital.
The Duke of Edinburgh is undergoing medical tests for a pre-existing heart condition.
Her Majesty The Queen spoke to Chief of the General Staff General Sir Mark Carleton-Smith on Tuesday morning, in her role as Head of the Armed Forces.
The British military's support for UK communities amid the COVID-19 pandemic and its operational duties overseas were among the talking points.
Ninety-nine-year-old Prince Philip was taken by ambulance to St Bartholomew's Hospital in the City of London on Monday, following two weeks at the private King Edward VII's Hospital.
The duke, who turns 100 in June, has now spent 14 nights in hospital.
He was reported to be "comfortable" following his arrival and Buckingham Palace said "doctors will continue to treat him for an infection, as well as undertake testing and observation for a pre-existing heart condition".
Prince Philip was initially admitted to hospital on 16 February for a few days as a precaution after feeling unwell.
The Palace also said the duke was responding to treatment, but that his stay in hospital is expected to stretch until at least the end of the week.
In 2020, he handed over his role as Colonel-in-Chief of The Rifles to the Duchess of Cornwall during a rare public appearance.
Cover image: Her Majesty The Queen (Picture: MOD).