Without knowing who has created the works, people can bid for them on eBay until the auction, called The Big Art Secret, closes on Sunday. Proceeds from the sale will go to St Wilfrid's Hospice. Hockney's work is "an ink and colour crayon drawing on a postcard" and Emin has donated four postcards.
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Sunday's weather update for the east with Philippa
Sunday's weather update for the west with Philippa
Philippa has Sunday's weather for the east