Help! Complete loss of power

[Jackfaith75]

Have 2003 a4 3ltr AUTO quattro. Never had any problems. Driving fine today when engine cut out. No warning lights on dash. Won't start. Engine diagnostic shows no fault. RAC said symptoms of wrong fuel but it definitely has petrol in not diesel. Fuel pipes checked and no blockages. Any ideas???

[James]

Some kind of immobiliser fault?