51 plate Transit 2L Turbo Diesel problem?

I brokedown this weekend on a busy roundabout in the middle of the city. There was no warning, I went to set off from the roundabout and my engine had stalled and failed to restart. The RAC pulled me out of the way and eventually got me goin again. He was fiddling around in the fuel filter area, what i do know is the priming pump pushed down and stayed down and he had a job bleeding it but now it works like it used to. Is this problem now fixed or is it likely to happen again? Can I replace anything to stop this? I have an idea its a problem with the fuel filter top bit, not the filter itself as he checked it. I'm so glad im in the RAC though. Thanks, Ben