Thanks, Tim for the reply. I saw those threads but what happened here is definitely not a case of condensation caused by the weather or water splashing in the dipstick hole. The cases in those threads seem to be relatively small amounts of water, or in the peanut-butter situation, the oil not being checked for a while. l'm hoping - not really expecting, but hoping - somebody has seen a massive influx of water in an hour's light motoring caused by something easily repaired.
One thing I will do tomorrow is pull the spark plugs and see if there is evidence of water in the combustion chambers. I'll post my findings then, as maybe another clue as to what the heck is going on here. Although I am afraid I know, but just don't want to admit it yet.
