Some years ago I had an assignment flying as Flt Mech full time out of Luxembourg with a 747 freighter. I spent a lot of time in the upper deck bunks as I would do round trip to places like Taipeh or Jo,burg. One night I was sound asleep in my bunk I suddenly woke up with a start - we have had a hydraulic failure. I went to the cockpit and had a look at all the hydraulic indications,which were fine. I told the F/E what had happened,we had a laugh at it then #3 system low pressure light illuminated,as I later found the pump had failed totally.I have no explanation why this happened,in a 45 year career nothing like this had ever happened before or since.At the time it left me a little nonplussed.