The Princess of Wales has completed countless engagements, visits and public appearance since she became a working member of the Royal Family. Over the years, she has cemented her ties to a wide range of organisations, charities and causes. However, these is one project which is particularly close to her heart, and it was a poignant visit tied to this which, Prince William revealed, has been one of her favourites.

The Princess of Wales founded The Royal Foundation Centre for Early Childhood, which researches and raises awareness around the importance of development in the first few years of a child's life. Earlier this year, the Princess took a trip to Italy to learn more about the unique approach to raising children in Reggio Emilia, as part of her work with the centre. Prince William spoke about the trip in a later radio interview with Heart Breakfast.

'She came back buzzing,' Prince William told presenters Amanda Holden and Jamie Theakston. 'I’m so pleased it went well for her.' He explained that Kate had been, 'looking forward to the Italian trip a lot' and that it went 'really well', perhaps thanks in some part to the amount of preparation the Princess did before she went.

'She wanted to do lots of research,' said Prince William. 'She’s a proper pro on early years so, most evenings, I’m fighting to get past the bedroom and all the paperwork she’s got lined up ready to read.' He added that he was 'so proud, very very proud,' of his wife and that she had been 'amazing.'

The Princess of Wales' visit to Italy was also her first official trip overseas since her cancer treatment and recovery, making it a doubly poignant visit. 'She’s been through so much in the last few years,' said Prince William, who also explained that visits like Reggio Emilia 'take quite a lot out of you because you’re on permanent receive the whole time.' He said that Kate was 'edging herself back in to more and more trips like that' but that the couple 'have to balance that [demand] and make sure she’s okay and rested.' Overall, however, Prince William said Kate was 'in good form.'

And the Princess' latest achievement certainly proves just that, as she was able to successfully complete a recent hike up Ben Nevis, Snowdon and Scafell Pike within the space of 24 hours (the National Three Peaks Challenge). Kate was raising money for The Royal Marsden Cancer Charity, connected to the hospital where she was treated.