Not had this happen before. Drove home from work last Friday no problem. Had tea, then gave my son and his GF a lift into town. Car started feeling sluggish as I was going round the ring road. As I came off the ring road and round to the railway station, the car could now barely move. Going out the back of the station, the car now ground to a halt and could only just keep running. It conked out, restarted it, it chugged for a few seconds, and then died again. From that point on, it would crank but not fire up. So I called the RAC out, he initially thought a fuel starvation issue, spreayed his can of stuff into the intake and still no joy. Moved onto ignition system, Spark was reaching the distributor. Needed to now check spark was reaching plugs. Undo the top timing cover to remove the top cover to get to No1 spark plug. Cover comes off and we both look at each other and say at exactly the same time "that don't look right". The left hand cam pulley had come undone and moved forward. The cam cover was the only thing that stopped the pulley (and Belt) coming off!!!! it now has a nice groove worn into the inside of it. The reason the car wouldn't fire up is that the distributor is driven off that cam, which was no longer turning as the cam pulley was just spinning on the cam shaft. Turned the crank by hand, tightened the bolt to pull the cam pulley back on and re-engage with the locating key and hey presto, the car fired straight up and off I went.
Of course the RAC guy didn't know it was a non interference engine, so he thought the gods were smiling on me that evening.