Prince Harry and Meghan Markle have made a surprise visit to a preschool in Los Angeles to plant Princess Diana's favourite flowers.The 35 year old Duke of Sussex's mum died following a car crash in Paris, France at the age of 36 on 31 August 1997.To mark the 23rd anniversary of her death, Harry was accompanied by his 39 year old wife as they joined young children to plant forget me nots in the preschool's learning garden.