aircon belt- no tensioner?

My '05 plate td4 has a belt to the aircon pump with no tensioner - has anyone come across this before? - could it have anything to do with the engine having been transplanted from a Rover 75 (I think)
As someone has cut the wires to the airco pump clutch I am guessing the aircon is not charged so I will probably just cut the belt off as I am not bothered with aircon any.

Should have a tensioner and even the R75 used the same tensioner setup so not sure why it's missing!

Buy one and some bolts and give it a whirl!