Hi need advice please, I have one of ‘those’ warrenties and they have just sent out an ‘idependant’ engineer to look at my 2007 tdv6 which had a catastrophic engine failure. Diagnostic is timing belt tensioner failure which has sheared off and destroyed the engine. Car has done 103k and belt was changed by a LR Specialist in 2014.....the warranty company is saying this is a common fault when not fitted properly....hence clearly looking to say it was a pre-existing fault and not covered!! Is this a fair one even after 4 years and 40k?? My limited knowlege would suggest not, but I’m no expert. The warranty company, though still looking at my case had suggested that I may have to make a claim through the garage who fitted it!!

I don't get your drift. But warranty company should pay out.

I wouldn't be mentioning a design defect.
The garage is unlikely to pay out after such a long time. And I don't think they technically did anything wrong

ask the warranty company to prove it was not fitted properly

continue with your claim under warranty and let the warranty company pursue the garage !! Never argue with stupid people, they will drag you down to their level and then beat you with experience.

If the belts were done 3 years ago, they can hardly claim it's a known failure issue. Tell them to pay or answer to the ombudsman.

These insurance companies need to be slapped about a bit.  2012 SDV6 - it's missing a couple of cylinders
2008 TDV8 - it was a labour of love and is much missed

Is this a case of the oil pump casing failing that is a well known issue with certain 2007 /VIN range?
If so, did the indi who changed your belts in 2014 change the oil pump housing? He should have been aware of this (probably everyone on this and Disco3 forum does) and should have discussed it with you. If you have the invoice of the work done, it may have the part specified as having been changed. If it has been changed, you can tell the warranty company to pay up, if not, best keep quiet.
Good luck.