Local residents of Rhyl, a seaside resort town on the north east coast of Wales, were severely affected by floods after a freak storm surge hit the area over three months ago.
The victims of the Welsh town were clearly on William and Kate's minds as they made their pledge towards the fund. The region holds a special place for the royal couple as they were based nearby on the island of Anglesey for four years when William was an RAF pilot.
"The Duke and Duchess realise that it is a long, slow and painful process for the many people displaced from their homes," a statement from Kensington Palace said.
"And as a token of their support, and to show the people of Rhyl that they are in their thoughts, Their Royal Highnesses would like to make a personal donation to Rhyl Town Mayor's Flood Appeal."
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Local mayor Andrew Rutherford confirmed the donation and thanked William and Kate for their kind show of support.
"I am delighted that the royal couple have taken the time to recognise that Rhyl was affected in the flooding and demonstrates their affiliation to places on the North Wales Coast," said Andrew. "It was a lovely and welcome surprise as well as a big boost to the Fund. Thank you William and Catherine, Duke and Duchess of Cambridge.
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Andrew added that the current total of the fund stands at around £50,000 and that William and Kate's generosity made a substantial contribution. He also accounted for other donations coming through, including one from the local Victory Club and another organisation.
More than 130 residents were affected by the storm surge that hit Rhyl in December. Many of those have been staying at holiday campsites and chalets in and around Rhyl while their homes are being repaired, and do not expect to return home until the autumn.