did a day trip in and out between high and low range several times throughout the day, got to one particular spot and needed low 4 areal steep down hill decent and thankfully when he tried for low the shifter seemed to be locked in high position, unlocked free wheelin hubs in front and had nothing so had to relock hubs so as it would move, we figure by this that the centre diff lock was locked on somehow reversed several times in case it was lockup but this did nothing, thats about it.
Pajero is fixed.
Removed console, removed hi lo range shifter from top of gearbox.
Reinstated shifter and all works great.
Think shifter jammed on guide plate in gearbox.
Hope it doesn't happen again.
Know how to fix it now.
Took longer to remove console and refit than to fix gearbox.
Thanks to all for comments and help.