You sounded the all-clear rather too soon, Melvyn The all-clear

I was jogging along nicely through the opening of Melvyn Bragg's new novel, Credo, when I was stopped by the following sentence:

A dry, trumpeting eruption signalled the all clear in his anus but still he squatted, superstitiously convinced that exposure to the freezing air might act as a natural stopper...

What is being described is a fictional Irish king, Cathal, and his troublesome diarrhoea. A few paragraphs previously, this complaint had been explored in details that we needn't bother with here, and I was thinking how brave Melv had been to tackle head-on an area of the human condition usually only glanced at by literature (eg "his bowels turned to liquid"). But the phrase "the all clear" broke my admiring reverie. Bragg's book is set entirely in the England and Ireland of the 7th century. Characters called Cathal and Padric jostle other characters called Bega and Ecfrith. It is not, I can safely say, a comic or experimental piece of fiction. What were the sirens of Dad's Army and the Second World War doing among the mead and the bogs?

A small thing, but it snapped the thread that was suspending my disbelief. Anachronisms always have that effect on me (perhaps they shouldn't but they do). I can just about forgive the 1950s steam locomotive in Ian McKellen's 1930s version of Richard III, and the corrugated-iron roof in Tony Richardson's otherwise 1700s version of Tom Jones. But I had great difficulty overcoming a dubious reference to some pub-bought peanuts in Pat Barker's novel Regeneration which is set in 1917. A friend of mine could never get over the wire coat- hangers which make their appearance among the Bletchley code- breakers of Robert Harris's Enigma. (Were there peanuts in pubs in 1917, and wire coat-hangers in wardrobes in 1942? Write to the Extremely Pedantic Old Codgers column, care of this newspaper.)

Trouble came just after East Croydon on the 20.50 from Brighton to Victoria last Wednesday. Three black boys ran through our carriage pursued by a white boy. The white boy said: "They've stolen my money, they've stolen my money." There were about half-a-dozen of us in the carriage and of course none of us did anything. For one thing the white boy looked a bit strange (drugs? care in the community?). For another, by the time we had worked out that a crime might have been committed and that it was anger and fear that made the white boy look strange, the black trio were already in the next carriage. So the white boy turned back and pulled the emergency chain. The brakes went on, the train stopped among the dark back-gardens of Thornton Heath. Leaning out of the window, I saw a carriage door open and the robbers jump down and skip along the tracks.

Pulling the chain was the wrong thing to do. The train was non-stop to Victoria, and if the victim had simply told the guard (if that's what they're still called) then the guard could have phoned ahead and had the police waiting on the platform, which is what also happened in this case, though by then the train contained no robbers to catch. Emergency chains are very crude devices; pull one and you automatically apply the brakes. They date from a time long before radio and mobile phones, when a woman stuck alone with a rapist in a non-corridor compartment had no other way to call for help, and when the train needed to be stopped before that help could arrive. Short of the direst emergency - murder, fire - you would these days almost always be better off waiting for help at the next station. But I suppose a notice grading emergencies and listing appropriate action - in case of heart attacks, summon the guard; for fires, pull the chain - is the last thing anyone in an emergency would want to read.

Does anyone doubt that OJ Simpson is guilty? The conventional wisdom is that a combination of race, money and fame got Simpson off the hook, and that his trip last week to the Oxford Union and Richard and Judy is a sorry indictment of our new amorality whereby we reward celebrity indiscriminately - good, bad or evil.

But perhaps the only new aspect of the affair comes from technology, from the television and satellites which have globalised the interest in it. Last week, prompted by Simpson's minimalist statement that he had "not been convicted of anything" and its echoes of Scotland's not-proven verdict, I re-read F Tennyson Jesse's account of the famous trial of Madeleine Smith. It has some interesting parallels with the Simpson case. For race, read sex. For fame, read beauty and youth. For the money to buy expensive lawyers, read ditto.

Madeleine Smith, the daughter of a wealthy Glasgow architect, stood trial in Edinburgh in 1857 for the murder of her lover. She was 21 at the time and her lover, Pierre Emile L'Angelier, 10 years older. Their affair had been passionate, physical (her torrid letters were the most sensational aspect of the trial, apart from the verdict) and secret. L'Angelier, a clerk from the Channel Islands on ten bob a week, was a poor prospect for marriage. Smith, who was also being wooed by a Glasgow merchant, decided to end the relationship, but her lover was persistent and at one stage threatened blackmail. Smith bought arsenic. L'Angelier died of arsenic poisoning. The court decided the case against her had not been proven, and she vanished to the United States, where in her old age she received distinguished visitors, including an older equivalent of Richard and Judy, George Bernard Shaw.

Nobody really doubted that she did it, but nobody seems to have minded much that she did. Her sex, looks and social status were on her side. And just as some of us tend to overlook Mrs Simpson, so we have forgotten L'Angelier, vomiting and crying his way to death in his lodgings and so much in love.