Two hundred people - women of seventy, boys of seventeen - spread over two measured acres of sandy beach and digging like mad through a hot summer's day. From time to time they had to be forced to rest, because their muscles, old and young, were driven by the hope that under the next shovelful of sand there might be a silver Maserati. or an E-type Jaguar, a Rover 2000. or a silver Cadillac, an ocean-going cabin cruiser, or a treasure chest containing £1,000. or any one of ten silver Mini-Coopers. Tonight Man Alive tells the story of the greatest treasure hunt ever launched in the name of commerce. It cost £150,000, and they called it ' The Big Dig.'