Simultaneous deaths

My grandparents were married for 50 years and never spent a night apart. They lived in a large terraced house with an adult son, and of course in at that time like most if not all the houses in the area they had no telephone. They were a bit frail and my mum used to pop in every day, often with me in tow, and bring them their shopping. In 1962 grandad suffered a stroke. This must have happened in the early morning after their son, my uncle, had gone on shift. My mum and I arrived at the house to find gran in distress and grandad on the floor beside the bed, not responding and breathing badly. Mum had to go out, find a phone-box and call an ambulance. He was taken to hospital. My mum stayed with gran and the rest of the family did turns at the hospital, over a few days. Late one evening, mum went to make a cup of tea and heard gran stand up, then sit down again heavily - she dashed back into the sitting room but it was clear that gran was dead, still sitting in her chair. No phone in the house - mum had to get her coat on and dash down the road to find a phone box, fiddle with change in the dark, and so on. She got the doctor's then called the hospital to tell the family - only to be told grandad had died 'just then'. There was an inquest and the coroner reckoned they died miles apart within 20 minutes of each other.