Please help, me

I have a problem with my 4x4 saff, I was driving the car and it was fine, then it suddenly cut out as I was changing down the gears, I bump started it, as i was moving and it ran for about 30 secs, then cut out again.
Now when I turn the key to start it, it fires and runs for about 2 seconds, then cuts out.
Any ideas what the problem is as I need the car for Stratford tomorrow.

P.S The car has not been started for three weeks, and it had a flat battery, is this anything to do with it?