In a move that was sure to please the ferry companies servicing the English Channel, a motorway under the sea between Britain and France was mooted last week in a study issued by Eurotunnel Plc on a second cross-channel link. Almost 200 years after a Channel road link was first presented to Napoleon by French engineer Albert Mathieu, Eurotunnel's study envisages cars zooming along a four-lane highway. But with the existing rail tunnel struggling to make money, a new one may never happen.