megane cabriolet engine noise then dead

As above, a cabriolet 1600 2005 I think, app 60,000 + miles has for the last while juddered and rattled mechanically a little bit when moving off but drove very well, quiet, no rattling, misfires,vibrations or smoke out the exhaust but would sometimes stall with a real chug at low revs. Has always had oil. Today it suddenly began to really rattle, the noise appearing to come from under the car, I thought I'd been dragging something under the car. Stopped the car. Nothing underneath it, no oil leaking so started it again and it was definitely rattling from the lower engine. Turned it off, made a phone call, turned the key in it again and it wouldn't start at all and hasn't since. In gear the starter will chug it forward so it's not that.

So I'm guessing a bearing problem or similar but does the non-starting indicate a clue as to what is wrong