During the engagement, the Queen met with General Sir Nicholas Carter, who is stepping down from his role of Chief of the Defense Staff, Buckingham Palace said.
Queen Elizabeth wore a floral dress for the occasion, as she met with Carter, who was in his military uniform, at Windsor Castle.
The Queen's health became a topic of conversation last month, when she canceled her trip to Northern Ireland on the advice of her doctors.
"The Queen has reluctantly accepted medical advice to rest for the next few days," a spokesman for Buckingham Palace said at the time. "Her Majesty is in good spirits and is disappointed that she will no longer be able to visit Northern Ireland."
A source added of the Queen, "She has had a packed schedule recently. She is resting at Windsor castle on doctors' advice but in good spirits."
Shortly thereafter, the Queen spent a night in the hospital. At the time, a Buckingham Palace spokesperson told ET that the Queen was in the hospital for "some preliminary investigations." According to the spokesperson, Queen Elizabeth returned to Windsor Castle the following day at lunchtime and was in "good spirits."
Then, on Nov. 14, the Queen missed the Remembrance Day service in London due to a sprained back.
"The Queen, having sprained her back, has decided this morning with great regret that she will not be able to attend today’s Remembrance Sunday Service at the Cenotaph," Buckingham Palace said in statement. "Her Majesty is disappointed that she will miss the service."
A royal source also told ET that "it is obviously incredibly unfortunate timing, and nobody regrets the Queen’s absence more deeply than her Majesty herself."
"Her Majesty is deeply disappointed [she missed] the engagement which she regards as one of the most significant engagements of the year," the source said. "[She] hopes to continue as planned with her schedule of light official duties."