King Charles III on Sunday was seen publicly for the first time since Buckingham Palace announced last week that he was being treated for cancer, strolling into a church on the royal Sandringham estate where he has his residence.

Charles, 75, waved and smiled at well-wishers who had gathered nearby to capture a glimpse of the monarch as news cameras flashed. He walked alongside his wife, Queen Camilla, before heading into the 11 a.m. service at St. Mary Magdalene Church.

Later, both the king and queen smiled and waved for the cameras as they headed back to their home at Sandringham House.

In a message released by Buckingham Palace on Saturday, King Charles thanked the public for supporting him since the news of his cancer diagnosis was announced.

“As all those who have been affected by cancer will know, such kind thoughts are the greatest comfort and encouragement,” he said.

The king added that it was “equally heartening to hear how sharing my own diagnosis has helped promote public understanding and shine a light on the work of all those organizations which support cancer patients and their families across the U.K. and wider world.”

Last month, Charles was admitted to a hospital for a routine operation to treat an enlarged prostate. But on Monday, the palace announced that during the course of that treatment, an unspecified form of cancer had been discovered. He has begun treatment for cancer and paused his public engagements during that time.

The king is currently staying at Sandringham, about 100 miles northeast of London.

The decision by the palace to disclose to the public that the king, Britain’s head of state, was being treated for cancer provided a rare candid insight into the health of a monarch.

But it has also left many questions in its wake, with little clarity on the seriousness of his illness or how long he will be receiving treatment.