Good news! PROBLEM SOLVED. The Alfa 156 was taken by RAC to the local engineering co. 2 m away and the guy had a look at it and found the solution almost immediately. The battery was not properly wired on the + terminal. Both RAC men and myself didn't spot the faulty connection. The engineering guy did. Well done, boy! No costs involved for me. Had I asked RAC to take the car to the recommended garage in Reading, I don't know what would have happened to the bill. I was well advised to choose the modest but efficient workshop in Winnersh, called Wingfield Engineering Ltd. Next time I will use my newly purchased jump leads without taking out any battery as I always have two cars parked side by side.
Many thanks to all clever members who contributed wisely to this thread.