As the winter sun dips over the affluent tree-lined suburb of Westridge in Rawalpindi, the only sounds are the calls of a pair of green parakeets and the banging of a wooden door.

The neat grey and white villa at 18a Nisar Road is typical of the spacious two-storey houses, most of which are inhabited by army officers stationed in the garrison town. But at the end of a drive lined with carefully tended pot plants, the front door has been torn off the lock.

It was here that the Pakistani authorities say they captured one of the world’s most wanted men, the Al-Qaeda operations chief Khalid Sheikh Mohammed, sleeping in an upstairs room last weekend.

The substantial villa, the cage of budgerigars on the terrace, the army dog-training centre backing onto the property — all present an image of respectability. Indeed, it is the home of a Pakistani establishment family that denies harbouring Khalid.

There are suggestions that the bulky 38-year-old terrorist chief was really seized elsewhere weeks ago — his arrest kept secret while CIA men attempted to pump him for information that might lead them to their ultimate goal, Osama Bin Laden.

Whatever the truth, the man who organised the September 11 attacks in America is now under intense interrogation in the secret facilities that the CIA has installed at Bagram air base in Afghanistan.

Asked if Khalid was talking, one American official said last week: “Absolutely . . . it’s as good as it gets.”

But who is Khalid Sheikh Mohammed? Why is the arrest of the man known as KSM or “the Brain” so significant? The answers lie not just in his role in Al-Qaeda but in the life he has led as a member of a family permanently at war with the West. On occasions Khalid could behave more like a playboy than a religious fanatic; but terror was his birthright.

IT IS 1,500 miles from suburban Rawalpindi to the extravagant shopping malls of Kuwait City at the head of the Persian Gulf. This is where Khalid was born.

He was not, however, one of the rich Kuwaitis. His childhood home was in a down-at-heel suburb called Fuhayhil, near the terminals where giant supertankers load their cargoes.

With its poorly built housing and lack of amenities, Fuhayhil was one of several towns built by British oil companies in the 1950s to house the thousands of migrants who worked in the refineries and pipelines and in the service industries that grew up alongside them.

Many of the migrants were Palestinian refugees, but there was also a large number of Pakistanis — among them a man called Shaikh Mohammed Ali from Pakistan’s “wild west”, the province of Baluchistan.

Baluchis have for many years had a special relationship with the Arabs of the Gulf, who regard them as “cousins” and allow them to travel freely in the area without visas.