Those who go public with their family histories tend to be the famous (remember Germaine Greer's quest for the truth about her father, Daddy, We Hardly Knew You) or writers who feel that their origins seem to offer reflections of wider moment than the personal. The weakness of Arnold's book is that for too long we place her in the first category, though jibbing a little at the idea that a mere columnist should assume she is interesting enough for us to want to read about her embarrassment at looking less than Anglo-Saxon, her ancient uncles in Dawlish and her mother's ill-fated attempts to keep her end up among the suburban snobs of North London.
But at least she is laudably unpretentious, even self-mocking. And Burma (though Arnold likes to fight the fact) has always had a galaxy of glamorous associations - General Slim, Neville Shute, Elephant Bill. So we bear with her, enjoying the swift and skilful pen portraits of newly discovered relations, the adventure of her mother's trek across Burma as a refugee (straight out of A Town Like Alice), increasingly sympathetic to the plight of the mixed-race child.
Being turned away from Fifties boarding houses with "colour bars" and having your five-year-old knees lashed with nettles was bad enough; but to have Sir Adrian Boult complaining to the editor of the Observer in the Seventies about "wops" being sent to interview him must have been deeply humiliating.
Our patience is rewarded. For the book's strength is that, as Arnold gets into her stride, we realise that she is saying something very important indeed about the attitude we should be taking towards a country that deeply affected the lives of thousands of families in Britain (27,000 Allied soldiers died in the Burma campaign) and which is today balanced on a knife-edge between dictatorship and democracy.
Myanmar, as Burma is now called, is all set to be the latest of the glamorous far-away places lauded in holiday brochures - picturesque pagodas, the road to Mandalay, the Irrawaddy river. But it is a wolf in sheep's clothing, governed by a military dictatorship which is exporting teak and rubies hand over fist for private gain, and which has even sold native fishing rights to neighbouring countries. The tourist trails are hedged about with security guards; free speech is ill-advised. On her last visit, Arnold found her cousins suddenly mum; letters and presents went astray.
The change of name is a ruthless piece of public relations legerdemain: the generals seem to think that the flocks of tourists ripe for fleecing won't realise that this is the country in which university students were crushed in 1988 considerably more brutally than the Chinese students of Tiananmen Square, and in which Noble Peace prizewinner Aung San Suu Kyi, whose National League for Democracy party won a landslide victory in 1990, was placed under house arrest for five years.
Even now, theoretically free, Suu Kyi and her supporters are walking on eggshells. Many have been murdered, but many more remain. "There are too many people behind us for us to fail," said one of Arnold's cousins, elected as an NLD MP in 1990. Free speech may have temporarily crushed in Burma but international protests and the big stick of economic sanctions have made it necessary for the military government to don at least the trappings of democracy in order to board the gravy train of international trade.
The NLD's survival depends on the impetus towards open government which has been effected by economic pressure and liberal world opinion. In this context, Arnold's endearingly frank fragment of autobiography could prove invaluable.