Prince William has promised to “look after” his wife Kate as he returned to public duties for the first time since the Princess of Wales revealed she was battling cancer.

The Prince of Wales helped unload food and prepare meals in the kitchen at distribution charity Surplus to Supper in Surrey on Thursday (British time).

One of the volunteers, Rachel Candappa, 71, handed William two ‘get well soon’ cards addressed to the King and Kate.

The prince looked visibly moved by the gesture and thanked Candappa, saying “Oh, you’re very kind. Thank you very much.”

She told William to look after Kate, at which the prince placed his left hand on her shoulder and said “I will”.

Rachel Candappa hands two ‘get well’ cards to Prince William. Photo: Getty

Afterwards, Candappa told media: “I was at home at 8.30 last night and I thought I had to do something. This is a chance to give a card directly to the palace officials. I didn’t think I’d be able to give the cards to William.”

Commenting on William’s heartfelt response, Candappa said: “He’s human after all. Remember he’s royal, but apart from royal he’s a husband, a father to the children, so he need to look after her.”

Prince William helps prepare bolognese for Surplus to Supper. Photo: Getty

In a video message last month, Kate, 42, the Princess of Wales, said tests taken following major abdominal surgery she underwent in January had uncovered cancer, something she described as a “huge shock”.

William, 41, has been absent from official engagements since then as the couple and their three young children come to terms with the effect of the news.

Although he and his eldest son Prince George were pictured watching their favourite football team Aston Villa play last week, Thursday marked the first time William carried out official public appearances since Kate’s highly-personal announcement.

He appeared in good spirits as he chatted and helped out staff on a visit to a surplus food redistribution charity.

“Reducing food waste has a considerable number of environmental benefits, including reducing emissions from landfill that contribute to climate change,” the palace said.

“Protecting the environment for future generations is one of the Prince of Wales’s key priorities.”

William later visited a youth centre that receives regular deliveries from the charity.

The King is also being treated for an unspecified form of cancer.

Kate, often referred to by her maiden name Kate Middleton, will return to public duties herself when her medical team say she is well enough to do so, her office has said. No timescale has been given.

Her illness comes at the same time as the King has been absent from public duties since his diagnosis.

However, he did greet crowds during a walkabout after an Easter church service at the end of March.

-with AAP