The picture that depicts the Queen's loneliness

The Queen had an incredibly busy schedule last week, with President Trump’s state visit, the 75th anniversary of the D-Day landings and Trooping the Colour to mark her official birthday.

The 93-year-old has shown no signs of slowing down, with Hello magazine reporting that she has already carried out 28 days of work this year - more than the Duchess of Cambridge and Duchess of Sussex.

“I think she made this pledge that she would serve her country until she died and she’s just going to keep it,” royal biographer Angela Levin tells Yahoo UK’s ‘The Royal Box.’

“She looks amazingly healthy, she’s very articulate, she’s very energetic, she stands up for an hour.”

But Levin noted that the Queen looked lonely at Trooping the Colour on Saturday, without the Duke of Edinburgh, who retired from public duties in 2017.

READ MORE: The Queen only saw her children for around 20 minutes a day, says royal biographer

Queen Elizabeth II makes her way from Buckingham Palace to Horse Guards Parade, in London, ahead of the Trooping the Colour ceremony, as she celebrates her official birthday.
The Queen makes her way from Buckingham Palace to Horse Guards Parade during Trooping the Colour. [Photo: PA]

She says: “I felt a little sorry for her when she was in her coach, because she was entirely on her own.

“Quite understandable that Prince Philip didn’t come at nearly 98, but it was quite lonely and I thought, this is the loneliness of the monarch.”

The younger members of the Royal Family often accompany Her Majesty at official engagements now.

The Queen also cut a lonely figure last Christmas as she travelled to her Sandringham estate by train. It’s believed the duke was driven to Norfolk instead of taking public transport.

Former royal editor Duncan Larcombe says: “A lot of people think that perhaps she might stand down once her husband the Duke of Edinburgh passes away. That is certainly a possibility.”

READ MORE: The Queen handled Donald Trump's state visit 'beautifully'

Queen Elizabeth ll arrives at King's Lynn train station for the start of her traditional Christmas break at Sandringham in Norfolk on December 20, 2018.
The Queen arriving at King's Lynn train station last December without Philip. [Photo: PA]

But royal producer Nick Bullen told ‘The Royal Box’ on a previous episode that he thinks the Queen will never step down as monarch because abdication is now seen as ‘a dirty word in the royal household’.

Elizabeth’s uncle Edward VIII caused upheaval for the firm when he abdicated the throne in December 1936, less than a year into his reign. He sparked a constitutional crisis when he proposed to American divorcee Wallis Simpson.

After Edward stood down, the Queen’s father, King George VI, became king despite having never anticipated that he would be monarch and making the then Princess Elizabeth heir to the throne at the age of 10.