CAPE TOWN - Britain's Prince William said on Wednesday his wife Kate was doing "really well" and had been amazing in a year when she has undergone preventative chemotherapy for cancer.

The British heir to the throne is currently in South Africa where he hosted the annual awards ceremony for his multi-million-dollar Earthshot Prize. He made the trip without Kate who is still recovering from her treatment.

Speaking to the BBC ahead of his environmental prize's awards ceremony in Cape Town, he said she would be cheering him on from their home in Britain.

"She's doing really well thanks," he said in the interview. "She's been amazing this whole year. I know she will be really keen to see tonight be a success."

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As well as Kate, he said he hoped their three children, George, 11, Charlotte, 9, and Louis, 6, would also be watching on proudly, saying they as a family did what they could to help the environment.

"We go through all the basics of recycling and making sure we minimise water use and turning off lights when we leave the house and stuff like that," he said.

William set up the Earthshot prize to find innovations to combat climate and other green issues in 2020, inspired by US President John F. Kennedy's 1960s "moonshot" project which led to the 1969 lunar landing. Five winners receive 1 million pounds ($1.3 million) every year to drive their projects.

"I believe our world can be rich in possibility, in hope and in optimism," he told the awards ceremony. "That is why the Earthshot prize exists - to champion the game changers, the inventors, the makers, the creatives, the leaders."