The Queen has visited Salisbury Cathedral in her first public appearance since King Charles' cancer diagnosis.
Queen Camilla was speaking on Thursday at a concert raising funds and celebrating the work of local charities at Salisbury Cathedral in Wiltshire.
Buckingham Palace announced the King's cancer diagnosis on Monday.
The event saw the award-winning concert pianist Rupert Egerton-Smith as special guest artist, in performance with The Band of The Grenadier Guards and The Band and Bugles of The Rifles.
The Band of The Grenadier Guards represent the most senior infantry regiment of the British Army, while the Band and Bugles of The Rifles represent the largest sole rifle regiment in the British Army.
Asked how the King was doing at an event at Salisbury Cathedral on Thursday evening, she said: "He is very touched by all of the letters and messages the public have been sending from everywhere."
"That's very cheering," she added.
Among those she spoke to was a members of the Wiltshire Air Ambulance team which she is a patron of.
Paramedic Ben Abbott, who said: "I do hope His Majesty is doing well Ma'am, we're all really sad to hear the news."
Aware that the Queen has a house in the village of Lacock, Wiltshire, Mr Abbott added: "I told her we always wave when we fly over Lacock and she said she always waves back."
Trainee specialist paramedic Matt Metcalf said the charity needed £4.5m to keep delivering lifesaving care.
He said having the Queen's support was a "real privilege and honour".
"We are really proud and honoured to have her as our patron," he added.
The Queen also met representatives from a number of other charities including the Colonel's Fund Grenadier Guards, before enjoying a private concert with guests, compered by Paul Martin, host of BBC's Flog It!.