Queen Camilla admitted she was still feeling “a bit tired” as she attended a reception to mark the 50th anniversary of Women’s Aid despite her recent pneumonia diagnosis.

Her Majesty, 77, revealed on Tuesday that her chest infection was a form of pneumonia, which has forced her to scale back her work schedule. She is suffering from post-viral fatigue and is being urged by her doctors to take more time to recover.

The Queen skipped the outside elements of the Qatari state visit earlier in the week to avoid standing outside in chilly temperatures for a prolonged period of time.

But she joined the King and his guests for lunch at Buckingham Palace, an exhibit and the state banquet in the evening.

On Wednesday she undertook two engagements, and today she met survivors of domestic abuse and supporters of Women's Aid at a star-studded reception at the Institute of Mechanical Engineers, just a stone's throw away from Clarence House

When guests enquired about her health, the Queen said: “I am still a bit tired. It catches up a bit”.

Many attendees congratulated the Queen on the success of her recent ITV documentary, Her Majesty the Queen: Behind Closed Doors, which explored her many years of work in the field.

One of the survivors who took part was Alice Liveing, who was abused by her partner at the age of 16.

Miss Liveing, who is now a Women’s Aid ambassador, said: “I asked how she was feeling. She said she was feeling pretty tired but was trying to juggle some bits.”

During the reception, Camilla hailed the strides made by the charity over the past five decades.

Making some impromptu remarks before cutting a cake, she said: “If you think what's happening now compared to what was happening 50 years ago, you must all be incredibly proud of yourselves.

“I think so many people hadn't realized what domestic abuse was, especially then. It’s terrible that after 50 years, it still hasn't been eradicated, but we are making progress.”

The Queen added: “I have no intention, now that I’ve started, to stop and I am determined to put an end to this.

“We have all got to pull together. You are all doing a wonderful job, and we will put an end to it, probably not in my lifetime, but in some of yours.”

The Queen told one guest: “I can’t support a charity just for the sake of it, I have to feel it.”