I take it this is the rear wheel drive 2.4tdci,it is a very long belt with numerous pulleys and usually draw a diagram of the route before removing. I take it you are levering the spring loaded tensioner pulley fully back,it sits just below the P.A.S. pump,think it is a 1/2"drive,if you are then if I remember there were two belts for these depending on the model etc and one was slightly shorter than the other and would verify the correct belt is being fitted. Good luck.
cdc
June 2016