The Queen is known for her robust health.
Her son the Duke of York once described her as being incredibly fit for her age, and the 92-year-old monarch still rides her Fell ponies at Windsor, and drives, mainly around her private estates.
But she still has a busy diary of events, and in 2017 carried out 296 engagements.
It was the first time that the Queen, as head of state, had watched the ceremony from a nearby balcony, and was seen as a sign of the royal family in transition and an acknowledgement of her age.
The Queen was not well enough to attend the Christmas Day service at St Mary Magdalene church and also missed the New Year’s Day one.
She later described it as a “particularly grisly mixture of cold and flu”.
She turned 90 in 2016 and, the same year, used the lift rather than stairs to enter Parliament for the State Opening, avoiding the 26 steps of the royal staircase at the Sovereign’s Entrance.
The decision was attributed to the Queen suffering from knee pain.
In 2014, the Prince of Wales stood in for the Queen for part of the Order of the Bath service to avoid her having to make an extra journey up and down some steep steps in full regalia.
In November 2013, the Duke of Cambridge stepped in to represent the Queen at an investiture ceremony after she suffered some “mild discomfort” with her ankle after a busy weekend of engagements including the service of remembrance at the Cenotaph.
On March 3 2013, she was admitted to King Edward VII’s Hospital to be assessed.
A week of engagements, including a two-day trip to Rome, was cancelled.
The Queen spent one night in hospital and left thanking staff and smiling before being driven to Buckingham Palace to rest.
It was the first Commonwealth Day Observance service she had missed in 20 years, the last occasion being when she had flu in 1993.
The Queen, who placed great importance to her role as Head of the Commonwealth, did however attend the Commonwealth Reception at Marlborough House on the evening of March 11 to sign the new Commonwealth Charter.
Buckingham Palace insisted it was just the “tail end” of the symptoms and that her condition had not worsened.
But the next day she cancelled her engagements for the rest of the week, with her son, the Duke of York, saying later that it was sensible not to risk her coming out, but that she was not ill.
Her illnesses have been few and far between over the years.
She has suffered from back pain, and also had operations to remove torn cartilage from both knees.
She caught measles when Prince Charles was two months old in 1949 and had to be separated from her baby son.
The first time the Queen was actually admitted to hospital was in July 1982 when she had a wisdom tooth extracted at the King Edward VII Hospital in central London.
The Queen’s no fuss approach to injury and illness was perfectly illustrated in 1994.
She broke her left wrist when her horse tripped during a ride on the Sandringham estate in Norfolk.
It was the first time she had fallen in many years and the Queen had simply brushed herself down, remounted her horse and trotted on back to Sandringham.
