Thanks to David Marks for pointing out this repair kit is available for the oil cooler pipe on an XJ81. It is listed on SNGB’s site but it isn’t referenced on the picture so easy to miss. The O rings had gone hard and it leaked when parked. The tool shown bottom right purchased from eBay wasn’t long enough to lift the gripping fingers off the pipe so I used a pair of Talbot 20 mm MDPE extractors I had in my plumbing box and they worked perfectly. The fitting is on RHS front just behind the valance.
Is the oil cooler on the V12 car a twin circuit type, ie does it cool both the engine oil and the transmission fluid?
I think the auto box cooler is part of the radiator. The engine oil cooler is a separate unit.