Inside the villa in Rawalpindi where police say they arrested Khalid, an old woman sobbed gently, shoulders shaking, as she gathered a black shawl around her head and across her mouth and nose so that only her eyes were visible.

Mrs Mahlaqa Khanum is the mother of Ahmed Qadoos, the 42-year-old Pakistani accused of sheltering the mastermind of the September 11 attacks. Qadoos was arrested in the raid on the house that police say netted Khalid and another top Al-Qaeda suspect.

The family is no stranger to controversy. Qadoos is a cousin of Dr Hasnat Khan, the Pakistani heart surgeon with whom Diana, Princess of Wales, was said to be in love. But Khanum said any idea that her son was sheltering terrorists who are on the FBI’s most wanted list was “impossible”.

Pointing at a large cage of blue and green budgerigars on the terrace, she said: “These are his life. Ahmed is a very simple person. He had no job, he hardly went out, just to the mosque to pray. He never travelled and his main thing was pets. He loved pets. We wouldn’t let him have a dog because we’re an Islamic family, but he loved his budgies.”

Qadoos would watch the army dog-training centre behind the house for hours. His mother produced a medical report describing him as a “low IQ person” and a letter about his condition from the Food and Agriculture Organisation (FAO) for which her husband, Dr Abdul Qadoos, a microbiologist, worked for 30 years in several countries.

A heart bypass operation forced the doctor to retire in 1985 while he was in Zambia. Now he is managing director of Hearts International, a cardiac hospital in Rawalpindi, although his own heart condition has made him frail.

The description of Qadoos as a simpleton is supported by the family’s neighbour, Colonel Shahida of the Pakistani army.

“Ahmed can’t be a terrorist,” he laughed. “He’s a goof, simple in the head. Once he shot himself in the hand because he was cleaning a gun with the barrel against his palm. They are a purdah-observing household. We never saw anyone strange enter the house.”

Kkanum and her husband were at a wedding in Lahore when their house was raided. Ahmed Qadoos, his wife and their two children Aisha, 12, and Bilal, 8, were sleeping in a downstairs room when they were woken by a loud bang. The door was forced open and about 25 police officers rushed in.

Qadoos’s wife said she and the children were pushed into a spare room and told to remain silent, guarded by an armed policeman, while for more than an hour officers ransacked the house.

“We were petrified,” she said.

When they left she called her cousin, Dr Surbuland, who lives in the next street. “It was about 4.15am. She was very confused and at first we thought Ahmed had been kidnapped because they had taken some dollars,” he said. “Everything had been turned upside down.”

The family have been given no information since then and were horrified to read in newspapers that Qadoos had been charged with sheltering a terrorist. “I’m so worried for him,” said his mother. “He was taken in his vest with no shoes, nothing — and he had flu.”