[chrisjp]

The battery had gone flat,never even considered that as i'd driven it there & had no previous clue/hints as to battery condition

Yes, modern batteries do seem to fail completely suddenly - you can drive up quite normally, turn off the engine, come back in half an hour and the car is completely dead. I've had it happen to me.
A few years back batteries would always provide warnings of their demise - slow cranking when starting, headlights dimming as engine speed decreased etc.
This just doesn't happen any more.