Afterwards, as a thousand times before, he would have handed his scripts to his producer, bade him or her goodbye with a cheery “God bless” and walked away. No doubt his hand was already reaching into the pocket of his hallmark striped blazer — a garment he sported summer and winter alike — for a Benson & Hedges “gasper”. My cough sweets, he used to call them.

What John could not have suspected, nor the millions of listeners who heard his familiar delivery that January day, was that one of the BBC’s best-loved voices was only 48 hours from catastrophe.

Early on February 2, 2000, while he was still in bed, a blood clot entered John’s left carotid artery, one of the two main supply routes of blood to the brain, and blocked it. This interruption caused what he was soon to learn was a cerebrovascular accident, or CVA. To you and me: a stroke.

And what a massive stroke it was. At 51, his relative youth played as much of a part in saving his life at that moment as his heavy-smoking, sedentary existence behind the microphone had in almost costing it. He had survived, but at a terrible price. For in those first painless but terrifying minutes that followed, John realised that he could not move, swallow — or speak. The voice, described by one listener writing from Uruguay as “the mightiest voice to hit the airwaves”, was gone.

An ambulance was sent for. Its doors were closed while the paramedics did their assessments. Then the blue light was switched on and John’s unimagined journey began.

It is often said that death is the great leveller, but sudden, critical illness has pretty much the same effect. From the moment he entered the hospital system, who John Stone was ceased to matter. The loss of speech is very common in stroke victims, of whom there are 100,000 in Britain every year. He was told that he would have speech therapy in the months to follow and a level of ability would return. More pressing was the need for John to rest while the bruising in his brain subsided, after which scans would reveal the extent of the damage.

A broken ankle that leaves you with a permanent limp is not, on the scale of things, a great tragedy — unless you are David Beckham, or Darcey Bussell. And a nasty accident with a hedge trimmer that robs you of half a finger is not the end of your life — unless you are Nigel Kennedy. Trying to explain to people — consultants, nurses, anyone who would listen — how devastated John would be feeling as a broadcaster, whose voice was his livelihood, proved pointless. He would be treated as anyone else. Teaching him to eat, with puréed food, and drink, with synthetically thickened tea, was a priority. Getting him to stand, another. To regain bladder control, a third. Relearning communication skills was on the list, but nowhere near the top.

John’s eloquence had prompted the late Leo McKern to write in a letter to him in 1995: “In these days of ‘sekkatrees’ and shipwrecked syllables, your speech stands like an Eddystone”. Now he could barely grunt. Many a night in those first six weeks of John’s time in hospital, when I had to leave him drooling and silent in his chair at the end of visiting hours, I would get only a mile or so into the icy dark before I was so blinded with weeping that I had to pull over.

His first consultant was an original Job’s comforter. I managed to secure a meeting with him five days after John was admitted. Only then did the enormity of what lay ahead begin to sink in. We were talking wheelchairs, ramps, hoists. It would be a long time, if ever, before John could drive a car. It was unlikely that there would be more children; it was impossible to say what function would return, he explained dryly.

I learnt that when the brain is damaged, cells expire. But others can take over, mirroring the behaviour of the dead ones. Our brains can, in effect, rewire. How successfully, how completely, is never predictable. It is better to be realistic than to hope for too much, I was told. And probably best not to tell John the whole picture.

I had two responses to this prognosis. First, the consultant was wrong. He didn’t know John, he was reckoning without the character of the man I loved and admired. And John had so much to come back for; we had had only three years together. Our son was eight months old. Life had delivered these gifts relatively late. Surely it couldn’t be part of the plan to give them back? The twin reaction was an utter body blow. To know, in truth, that my blithe spirit and capacity to adapt to change was up against this reality: that the person I had known was already fundamentally altered and might actually be lost to me, and that our only hope lay in a long, hard haul.

Exhaustion dominated those early days. John now admits that it was hell. A speech therapist turned up one day with a piece of A4 paper, drew a line down the centre and wrote “yes” on one side of it and “no” on the other. John was to try to communicate by pointing to the appropriate word. He remembers the fury he felt at being unable to do even this. “I knew the answer,” he recalls, “but I couldn’t put it in the right column.”

Explore Health

• Expert Advice

• Health Features

• Mental Health

• Alternative Medicine

• Child Health