OK, I was wrong. The W8 tensioner (as an assembly) does swing to loosen like other cars I've worked on. But the tensioning unit itself is a separate piece, unlike others where the arm/pulley/spring are all in one unit. At least it looks that way, don't know if there's a spring in the arm and the little cylinder is a damper or something.
When I say "right" I mean looking at the front of the engine, toward driver's side (LHD.)
Find the crank pulley. Just to the right and a bit higher is the tensioner pulley. Above that and slightly right is a small bolt head. Look farther behind this small head and there is a 30mm head that you turn clockwise to give slack in the tensioner and remove/reinstall the belt.
The book says put the front in service position. Not sure if it can be done without that, but it would be a tight fit.
As far as the prying you mentioned, maybe someone found a way to do this with a bar instead of a 30mm socket and breaker bar. Personally I'd just use the right tools, but knowing how the tensioner moves, maybe there's an alternative.