Long popular with shipping magnates, including members of the Niarchos family, the region has recently attracted a growing number of the wellborn and the well-heeled, who love its unspoiled coastline and easy access to stylish islands such as Spetses and Hydra.

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Officers earlier concentrated their search around the coastline, including the small, offshore islands off the north-east coast, known as the Houmets, which can be reached on foot at low water.

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Wales recorded the highest density of beach litter, with more than 2, 600 items found on every kilometre of coastline surveyed, followed by England, Scotland, the Channel Islands and Northern Ireland.

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Spain's Mallorca and surrounding islands bring in 11 times more international visitors than Sicily, even though the Italian island has a longer coastline, Mr. Gnudi said.

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