Kate Middleton and Mary Berry share a sweet joke at Back to Nature garden in Woking - best photos

The Duchess of Cambridge surprised guests as she joined Mary Berry at the Back to Nature festival at RHS Wisley in Woking on Tuesday morning. Kate, 37, returned to work as she opened the new site, which has been inspired by the original design she created with Adam White and Andree Davies for the Chelsea Flower Show in May. The Back to Nature Garden includes features from the original garden at RHS Chelsea, including the hollow log and boulders from the waterfall, as well as the wildflower meadow, hidden burrow and rolling hill from RHS Hampton.

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Both Kate and Mary joined children on a ride in a trailer pulled by a tractor through the grounds to the site of a Back to Nature Garden Festival taking place at Wisley until September 15. New elements include a "bouncing forest", where visitors can jump on trampolines surrounded by trees, two treehouses, linked via a walkway with slides, and a living willow pod. The garden at RHS Wisley will be a permanent feature for children and families to enjoy. The project for Kate has been part of her work on early years and how spending time outdoors can benefit young children. The Duchess even brought along her own children to play in the Back To Nature Garden before its grand opening this summer. The Cambridges released rare footage of Prince George, six, Princess Charlotte, four, and one-year-old Prince Louis helping their mum to collect moss, leaves and twigs to decorate the garden. Click through the gallery to see the best pictures from the engagement...

Kate and Mary met families supported by charities that the Duchess has worked with over the past eight years at the celebration, which features a vintage carousel, coconut shy, gardening activities, maypole dancing and circus acts. The two appeared to be getting on like a house on fire.

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Mary, who is an RHS ambassador, looked lovely in a chic floral dress, which she paired with pink shoes and a matching cardigan.

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The garden has been inspired by previous open spaces she co-created with landscape architects Andree Davies and Adam White, with input from the RHS. Sue Biggs, RHS director general, said: "We are grateful to the Duchess for the incredible impact that this Back to Nature collaboration has had.

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"There is no doubt that this project, through her passion and vision, has highlighted that access to natural environments and green spaces isn't just a nice to have, it's vital to have. This is something that the RHS also strongly believes in and will continue to champion through our Greening Great Britain Campaign and charitable work."

In a speech, Kate explained why she has been trying to encourage families to get back to nature. "I am not as green-fingered as many of you here, but I was passionate about creating a garden that inspired children and adults alike to get back to nature and reap the positive mental and physical health benefits that it can bring," she said.

"The gardens were, I suppose, a manifestation of some of the work I have been focusing on around how best we can support our children in the earliest years. The physical benefits of being outdoors and in nature are well documented. More recently, however, I have learnt that these often safe and supportive environments can also bring significant benefits to the cognitive, social and emotional development of our children too."

"The experiences we gain during our earliest years influence who we become as people. They influence how we interact in school, in work and in society and, ultimately how we bring up our own children," she added. Before she left, the Duchess was presented with a bronze sculpture of a sycamore leaf to remind her of her collaboration with the RHS.

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Kate's co-created gardens were previously exhibited at the Chelsea Flower Show and the Hampton Court Palace Garden Festival, with the aim of highlighting how time outdoors can enrich a child's early development.

Kate had a great time chatting to attendees. As ever, she showed off her maternal side when she stroked a 15-month-old Matilda Griffiths's head. Her mum, Sarah Griffiths, 25, from Southend, Essex, who has been helped by the charity Family Action, said: "She was just saying that her little boy Louis loves to smell flowers and he enjoys being out in the garden.

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"The experience was a bit overwhelming, it's still a bit of a daze, but really exciting. She asked me how Family Action have helped me. They've helped me lots getting me out socialising."

Kate was equally impressed by the face paint decorating three-year-old Dylan Corbin from Woking, Surrey, but perhaps got an unexpected reply. "Are you a tiger?" she asked. "No, it's face paint," he said.

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The royal looked pretty as a picture in a floral Emilia Wickstead dress, worth £1,635. She wore her hair loose and flowing and she rocked fresh skin and minimal makeup.

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New features of the garden include two connected tree houses and slides, which encourage families and friends to have fun together. It will become a permanent feature at Wisley.

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