A graffiti exhibition backed by Banksy has been shut after vandals daubed “f*** the King” on a building owned by the Crown Estate.The Long Dark Tunnel exhibition in Piccadilly was forced to close due to pressure from the landlord, after anti-monarchy graffiti appeared on the walls of the building and other Crown-Estate owned properties nearby.The exhibition, which opened last month, was created by graffiti writer 10Foot — real name Sam Moore — and featured in a special edition of the Big Issue which generated an estimated £500,000 for the magazine with record sales.