The heir to the throne hugged the pop star as he arrived at Maindee Primary School in Newport, South Wales.

Horner is an advocate of his Homewards project, the intention of which is to end homelessness.

She and the prince spoke to children who were working on art projects about what the word "home" means to them.

William said the school was "identifying early intervention opportunities" on homelessness and hoped its strategies could be "rolled out as best practice".

As she left the school, Horner said it was "amazing" and William was "lovely" and "kind".

She told staff earlier: "This is such a positive and inspirational school, and shows just how possible it is to tackle homelessness when everyone works together."

Homewards will be run by William's Royal Foundation with the support of high-profile people who will help with the work.

It is his first major initiative since he became Prince of Wales last year and admits it is a "big task".

Every night, 300,000 people in the UK experience homelessness, half of whom are children.

William wants to prove that collaboration at a local level can make homelessness "rare, brief, and unrepeated", citing Finland as proof it can be done.

He began the day at a mental health organisation called Mosaic Clubhouse in Brixton, south London, where he met Big Issue seller Dave Martin, 61, who he joined on his pitch in west London last summer.

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Each of the Homewards locations will be encouraged to develop action plans to tackle homelessness with up to £500,000 in funding.

Mr Martin said: "I think it's really personal to him. His mother used to go to The Passage [homeless charity] - that's where he experienced homelessness for the first time, that's why it's really important to him."

In Brixton, William tried his hand at being a barista at a stall run by an organisation which works with homeless charities training rough sleepers to make the perfect coffee.

Later, he used a lathe at a carpentry workshop run by Faithworks, a Christian charity that provides training for homeless people at St John's Church in Poole, Dorset.

In Newport, the headteacher of Maindee Primary School, Jo Cueto, said: "This project is crucial now to take stock of where we are in Newport and to find solutions though multi-agency working.

"It is clear Prince William is dedicated to doing just that and to, as he said, making it 'everyone's business' to make sure the most vulnerable in society are supported."

The prince is due to visit the other three locations on Tuesday.