P38 Cutting out

I just returned from holidays in Spain and France where the temperature was 38°C. I expierenced on two occassions, on the motorway, the engine of my P38 2.5 (160 000 km) Diesel just cut out and would not restart until about 1hr after. The temperature gauge on the dash was normal, no overheating warning anywhere. When I stop accelerating the engine stopped. Any clues could it be linked to the AC because on tickover with the high outside temp and the AC on it tick's over like a pig, with the AC off the tick over is ok.

Thanks

I had same sort of problem driving to north devon. Drove 197miles there it cut out. then 190 miles on way back cut out again. tested the delivery of pump in tank and while testing it the pump stopped when i tapped tank with hammer it startded again. so i changed pump.