How can I re-set my immobiliser / alarm in my Chrysler Voyager 2.5TD?

I used my Voyager "T Reg" to a petrol station. After filling up etc, tried to start the car but the "Alarm Set / flashing light" did not go out. The car started for 2 second's and then cut out. This happened twice and then it just would not turn over. Called out the RAC and they tried in various way's including disconnecting the battery etc, but this did not work. Finally, I was towed back home. I tried the main key, but that still does not work.