Writing an obituary is not just nerve-wracking but risky.

It is fascinating, however, that a send-off that seems reasonable to some, is deeply offensive to others. These people, one suspects, will not tolerate even the slightest hint that their idol might have had feet of clay, like everyone else. With their loss still acute, they are like mourners at a funeral, who expect a warm, uplifting eulogy that consoles and comforts. Just as the church or crematorium are not the place to list a lifetime’s defects and deficiencies nor, it seems, is the newspaper or the news bulletin.

As a result, the obituarist’s task is one of the trickiest in the trade. While it does not compare to the dangers run by foreign correspondents, it carries a high level of risk. The Sunday in August 1997 when the phone woke me at seven in the morning remains one of the most stressful of my career. It was the deputy editor of a newspaper informing me that Princess Diana had died, and telling me to get out of my scratcher – a technical term favoured by news desks in those days – and get cracking on her obituary. This being before the internet age, and with the newspaper’s library experiencing “technical problems”, I was at the door of Waterstones before it had opened to gather as many books on the royals as I could. What followed was a burst of typing that made Vladimir Ashkenazy’s fingers look as if they had been dipped in treacle. By day’s end, I had written almost as many words as Simenon thought necessary in a novel.

There could not be a better case than Diana’s for summing up the dilemma of encapsulating a complicated life whose tragic end has taken everyone by surprise. Some months earlier, a team of us had written tributes for the Queen Mother, well in advance of the day they would be needed. Many such notices lie for years in what’s known in the trade as “the morgue”, while their subject defies statistics and medical prognoses. Goodness knows what effect it would have on them if they knew their final summation was ready to go into print at the touch of a key. It would certainly spook me, but perhaps the great, the good, and the grandees who tend to fill these pages would merely take it as their due.

When someone dies far too young, however, the obituarist is as shocked and sad as everyone else. In these circumstances it is all too easy to slip into hagiography, and to airbrush unattractive or discreditable behaviour. Writing about Diana it was impossible accurately to assess or even address some of the woeful decisions she had made in the course of her far from happy life. Stark facts were the best one could do when covering some of the more inglorious moments in her tempestuous lifetime. Like many a journalist before and since, I left the less flattering episodes for a future biographer to handle. On such occasions, the old adage that journalism is the first draft of history is only partly accurate. A farewell written in the heat of the moment might reflect popular sentiment, but it often also omits many of the deeper, most important truths.

But even when writing about those who have lived long and productive lives, there is a tendency for hyperbole and exaggerated praise. It might be impossible to libel or defame the dead, but journalists rarely take advantage of the freedom to dish the dirt, or raise doubts and scandals. Not deliberately, that is. The story of the Scottish writer outed as gay in an obituary is legendary, especially since this information came as a revelation to his wife and children. Even now the so-called family friend who accidentally let this drop must wake in a lather of sweat at the recollection of such an embarrassing faux pas. Not surprisingly he was banned from the funeral.

And then there are situations where a tribute must address distasteful details that are yet to be confirmed. In the case of Leon Brittan, for instance, some newspapers referred only to the “rumours” that had plagued his final year. Others described his questioning by police after a woman claimed he had raped her, decades earlier. We will probably never know if he was guilty of this, or of covering up child abuse among the establishment while he was Home Secretary. Regardless of whether he was innocent on both counts, these doubts will stand forever on record. It is poignant and even tragic that at the end of his life, when he was not able to refute these allegations, his reputation was tarnished, possibly irreparably.

Life, though, is rarely tidy. The curriculum vitae of a notable figure is almost always chequered, whether by success and failure, scandal and glory, or simply by the court of public opinion. On their death, we might judge them kindly, but in later years reverse that decision.

Such revisionism, of course, is often the work of the biographer, who picks up where the obituarist left off. While theirs is a far more substantial job, it has the enormous benefit of being conducted with hindsight, in an atmosphere from which distorting passions have been removed. They also have time on their side, to interview rivals, enemies or colleagues as well as those who would not hear a bad word said about their subject.

Yet while the biographer enjoys a clearer perspective, far more people read obituaries. You might call them the poor man’s biography, the snapshot rather than the photo album. It also explains why they are so fiendishly hard to get right, for their author knows that grieving family and friends will be studying their words forensically the next morning. Wogan, however, would surely not have taken offence at any obituarist’s gentle cavilling. A master of self-mockery, I doubt he would have grudged them having a last laugh at his expense.