Borrowed an A3 sport back 1.9tdi 2007 model from a family member, started it fine this morning and then whilst stationary in traffic, the car without any warning, just cut out! Tried re starting and absolutely nothing, it was if an immobiliser had kicked in. Pushed it aside, and awaited recovery. AA man after several head scratches and said he hadn't come across anything like it, as the dash lights came on as norm, battery tested ok, fuses in tact. He then went to the starter motor and found that there was no power there at all. Stripping back a little of the outer insulation, he bridged the cable to a direct live, whilst the ignition was on and it started straight away, thus proving starter motor to be ok. Turned engine off and won't start again. Anyone heard of this or had this problem? Possible relay or a hidden fuse?