Reading Robert Peston's description of typing up his wife's last book, shortly after her death, the words blurred on the page.

Peston, not surprisingly, had the same problem.

When novelist and biographer Siân Busby died last September, it was five years since she was diagnosed with lung cancer. Despite this, she continued to write, even when the end was very near. As Peston reflects, her decision "probably seems slightly bonkers, but she – and I – had an important if not wholly rational conviction that where there is life there is hope, that there is no point living in constant fear, and that there is an almost moral imperative not to be ground down by circumstances, even if those circumstances are an express train thundering in our direction". What astonished her husband was not that she wanted to write, but that, given her condition, she managed to.

It's an interesting question. When a writer learns they have only a short time left to live, do they unplug the screen, or sit down to write with fresh urgency? Although the answer must depend in part on how ill they feel, it would not surprise me to learn that many take the route Busby chose, and carry on regardless.

Premature death was all too common in centuries past, a spectre at everyone's shoulder. A young writer's first novel, play or collection of poems might easily be their last, as he or she would be very well aware.

However, it is only in our own well-diagnosed times that the terminally ill have a fairly accurate estimate of the span remaining to them. Or, indeed, know for sure what's wrong with them. As shown by Iain Banks's account of going to his GP with a sore back and discovering he has advanced cancer, many writers in times past must have been even more startled by the arrival of their nemesis. Deep down, wouldn't most prefer it that way?

Perhaps not. When Anthony Burgess learned he had lung cancer, he set to writing with renewed vigour, to ensure his wife was left financially secure on his death. He felt it was the least he could do. One can see that the impulse to provide for others might be the best possible antidote to self-pity, morbid introspection or premature retirement. That, and the need to carry on as normal when, of course, nothing will be normal again.