What electrical fault could cause my fiat punto not to start?

I was driving my 2000 V reg fiat punto (1.2 petrol) yesterday. When I came to a junction the car suddenly cut out. When I turned the key to restart it there was a high pitched screeching noice like the car wanted to start but would not cut in. The battery is fine, the start motor is working and there is fuel going to the car. I am guessing it must be electrical as it suddenly stopped working. Any idea what it could be?