On Tuesday, the monarch hosted an event marking the retirement of her household's most senior official, former Lord Chamberlain Earl Peel.
Her return to work comes as preparations are under way for Philip's funeral, which will feature servicemen and women from the Royal Navy, Royal Marines, Army and RAF – alongside top military brass – this Saturday at Windsor Castle.
It was announced at the weekend that the monarchy and their households would enter a two-week mourning period, with members of the family "continuing to undertake engagements appropriate to the circumstances".
The Earl Peel's retirement comes after 14 years in the post, with his replacement Andrew Parker taking over at the beginning of April.
He had overseen arrangements for the Duke's funeral, known as Operation Forth Bridge, before handing over responsibility just a week before the royal's passing.
The Lord Chamberlain oversees all senior appointments in the household, is the channel of communication between the sovereign and the House of Lords, and ensures co-ordination between Buckingham Palace and Clarence House.
During the retirement ceremony at Windsor Castle, the Queen accepted her former aide's wand and insignia of office.
The event was recorded in the Court Circular, a daily list of the events attended by the Queen and her family.
It said: "The Earl Peel had an audience of The Queen today, delivered up his Wand and Insignia of Office as Lord Chamberlain and the Badge of Chancellor of the Royal Victorian Order and took leave upon relinquishing his appointment as Lord Chamberlain, when Her Majesty invested him with the Royal Victorian Chain."
Ahead of Prince Philip's funeral, Thames Valley Police are carrying out specialist searches around Windsor town, with officers examining street furniture including phone boxes, post boxes, drains and bins as part of the operation.
The force said it has put a range of visible and covert security measures in place for Saturday, when the Duke is to be honoured with a ceremonial royal funeral at St George’s Chapel.
The funeral will take place entirely within the grounds of Windsor Castle, reflecting the Duke's wishes and in accordance with plans approved by the Queen.
Tributes from across the world and Armed Forces have continued to be paid to Prince Philip since he died last Friday aged 99.
Cover image: The Queen and Prince Philip ahead of his 99th birthday last year (Picture: PA).