Queen Camilla admitted she is "trying to hold King Charles back" amid the monarch's cancer treatment.
The Queen revealed the King was "thrilled" to return to royal duties this week and joked that she had been "trying to hold him back" during his cancer treatment.
Camilla, 76, spoke about the monarch's dedication to his work during her reception at Buckingham Palace to relaunch the Wash Bags Project.
The monarch, 75, returned to public duties on Tuesday after doctors said they were pleased with his progress following his cancer diagnosis in February.
On Tuesday, King Charles, who has been a patron of Macmillan Cancer Support for over 20 years, made a trip to a London treatment centre.
Speaking to Teresa Tideman, chairman of In Kind Direct, the Queen said: "I think he was really thrilled to be out."
Giving insight into how Charles has been feeling the past few months, Camilla added: "I've been trying to hold him back."
In response, Tidman joked: "Good luck with that."
The King, who is still undergoing cancer treatment, was accompanied by the Queen, who is president of cancer support charity Maggie's.
The pair were presented with posies after meeting with staff and patients in the cancer centre.
Charles's engagement came after doctors gave him the all-clear to restart public events, and will likely raise awareness of the importance of early diagnoses.
The monarch also hoped the trip could highlight some of the innovative research supported by Cancer Research UK, which takes place at the hospital.
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On Wednesday, Camilla welcomed 300 guests at Buckingham Palace to recognise people who support victims of sexual assault.
Camilla, 76, also delivered a hard-hitting speech to attendees including Cherie Blair, Carrie Johnson and Theresa May in which she thanked them for "standing up and committing yourselves to bringing an end to these heinous crimes".
The reception was also held to relaunch her Wash Bag Project, which provides a wash bag of toiletries, donated by Boots and distributed by In Kind Direct, to people who have been affected by rape and sexual abuse.