Car has never missed a beat before.
Got in to start her after leaving her standing for three days and the car wasn't even turning over. Got my brother to come round with Jump leads, got her running, drove for a little while to my friends house. Drove fine on the way. Parked up and she was then left sat for about three hours.
Went to start her up again, so flat she wouldn't even turn over this time (usual dash lights dimming etc). Jump started again, got running fine. It was dark so had headlights on now. After about five mins whilst doing 40mph (maybe irrelevant), there was a slight jolt and the ABS light and Handbrake light came on in the display on dashboard. After that, the headlights flickered infrequently. The ABS and handbrake light came on again a little later but no jolt this time
Got home, turned car off and went to start her back up again, and the same happened again - she made absolutely no effort to turn over.
Car does reasonable runs, not just short journeys. Never had this trouble before. Would it be battery, or alternator?
Thank you in advance,