He did not cry — that was against the rules — but imagine the desolation of the 11-year-old boy: left in a strange school in a strange country as his father disappeared down the drive in the back of a green Vauxhall taxi. “I knew then,” says George Alagiah softly, “I would never live with my family again.”

So began a Sri Lankan boy’s British odyssey. Lately this journey has taken the BBC newscaster to some of Britain’s most racially divided outposts, prompting him to write a book with disturbing conclusions: Britain, he suggests, is becoming an apartheid state; but while in South Africa this was the design of whites, in Britain, Alagiah says, it is sometimes immigrants’ “own fault” they are “left behind”.

Just as the true level of immigration is revealed, this is provoking quite a rumpus. Alagiah says what third worlders despised about British colonists was their refusal to “learn our languages, eat our food or wear our clothes”. Now he accuses some of those colonising Britain of displaying precisely the same insensitivity.

Normally newscasters hide behind polished smiles — rarely writing books of greater controversy than eulogies to eccentric cats, etc — but A Home from Home (Little, Brown) is chewier fare. Alagiah, 50, insists his bosses at the Beeb are happy with his forthcoming book, but in this interview, sneaked during his lunch hour, he surely risks a caning for questioning the government’s policy of encouraging more faith schools.

Oh, and having tracked the only two white boys in a Bangladeshi-dominated school not far from his home in London’s East End, Alagiah suggests that natives can now feel as foreign in their own land as he did all those years ago on his first day in that Portsmouth boarding school; and that means feeling pretty blue.

“It went beyond homesick,” he recalls, deep brown eyes watering. “It was missing everything I had ever known.” It took two minutes to recognise his otherness; hearing other boys made him realise the flaws in “the English accent I thought I had perfected”.

But while many immigrants, encouraged by multicultural orthodoxy, retreat into their differentness, Alagiah cheerfully admits: “I spent the next seven years determined by the desire to fit in.” And while he agrees the “dislocation” of his childhood is no “template”, he is convinced that his successful career proves something: if you embrace your new country, it might embrace you.

This he has done unfailingly, even when confronted by the odd bigot; he just learnt to run faster than they could. He is married to Frances, who hails from well-to-do British stock. Her father warned that she would encounter prejudice but more than a decade later the couple are still together, with two sons who look suitably 21st-century London: indefinable.

For one whose job is to read an autocue, our George can sound a trifle self-important, describing himself as a “role model”; still, the lad has done good. A woman who saw him at a party recently purrs: “Utterly charming; spent ages chatting to my children.” He is, one suspects, motivated by nothing more evil than wanting immigrant kids to have the opportunities he enjoyed.

He admits that even for one with his elite education, an immigrant’s lot is not easy. At Durham University he was jolted when a fellow student saw a snap of his parents and expressed amazement they were Asian: “Before then I had come to think race didn’t matter, but that made me realise I hadn’t broken any barriers: I had simply switched over.”

For their and our benefit immigrants should, Alagiah contends, immerse themselves in British life: “Contribution is key. If you live in such an enclave that something as simple as language is getting in the way, you can’t make a real contribution.”

He was horrified to find politically correct schools providing parents with lessons in their mother tongues: “If there is any spare money,” he says acidly, “I would rather it be spent to teach them English.” As he concludes, with such policies it is hardly surprising that we are — by accident — revisiting apartheid.

Growing frustration at this ethnic division has profoundly changed attitudes to race, even within the liberal Establishment. William Hague was once condemned for his “foreign land” speech; but here is a senior BBC journalist echoing some of those sentiments.