Largest circumference tyres......normally the newest ones must without fail go on the rear of the hippo.
Keep to the same make and model on each axle and just swap them from left to right.
If they are all the same tyres and within 1-1.5mm you can get away with shopping corners.
Failure to stick to this on a hippo will result on your drivetrain destroying itself in the near future.

Hi All
Just an update, got the Hippo back after having the nearside rear drive shaft re fitted and the diff oil topped up, they have put the newer even worn tyres on the back and others on the front, I have only driven a few miles but it sounds a lot better, when I get around to changing the front tyres I'll get them swooped around again. Thanks for all the help.