Trying to change the alternator on my 2002 TDCI, I've managed to get the old one off but only managed to get the tension off the belt by undoing the bolt by the bottom of the alternator (it's the tensioner which is like a V shape with a pulley each end and a pivot point in the middle not the easier looking type which has the tensioner easily accessible at the bottom of the engine).

When I get the new alternator on, can I move the tensioner without buying a special tool that I've read about? Which way does the tensioner move, clockwise or anti?