Transport Secretary Grant Shapps today declared it is 'completely unsustainable' that P&O Ferries chief executive Peter Hebblethwaite remains in his job after sacking 800 seafarers without notice. The Tory minister also insisted 'they will have to pay the minimum wage' to crews as 'inexperienced' P&O agency staff paid £5.50-an-hour have been blamed for leaving one ship drifting in the Irish …