Yep to checking water pump. Viscous fan coupling sounds likely as well. Be fine idling but when underload/speed will slip and reduce cooling, so your temperature will go up. Will go back down when idling again.
For peace of mind would get sniff test done to make sure its not engine/hg failure. If ok, would then replace water pump, fan coupling and expansion tank cap.

darth510 said:

ok its been weeks now and no re-occurrence done over 200 miles and not one flicker of the gauge, spoke to a few LR enthusiasts who said mine is the 4.0 Thor engne and 'bullet proof! but i have only driven it normally! i will try putting it under load up a hill and see what that does. just dont have the trust back yet

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Hes obviously not a p38 enthusiast
The 4.0 thor engines about as bullet proof as marzipan
Needs treating like its on life suport especialy were its coolings concerned

lol I call them a glass engine,oh and its prob the becm failing first sign is usually temp guage false reading,load the electrics to see if it returns back to normal