His mother, Zakia Ahmed, said: “He travelled the whole night without any sleep.

“He has gone through much stress. He did not cry, I cried. We are all happy to have him back.”

Ahmed now faces questioning by Indian police investigating a banned Muslim group, the Students’ Islamic Movement of India (SIMI).

“It could be a routine investigation,” said a senior officer of the Corps of Detectives in Karnataka state. We want to examine his role before he left India.”

SIMI has been blamed for helping to carry out several bomb attack. Police arrested a medical student and a software engineer in Bangalore, following the arrest of the group’s leader Safdori Nagori and 12 other members in March.

Kafeel Ahmed wanted to kill hundreds of innocent victims and targeted nightclubs with explosive devices assembled at his home. 

Two bombs containing gas cylinders were concealed inside Mercedes cars and driven to London from Glasgow last summer. But the trigger units, activated by mobile phone, failed to go off.

One of the cars was planted in the early hours outside the Tiger Tiger club in London’s Haymarket, where 556 revellers were enjoying a night out. After the failure of the bombing mission, Ahmed, 28, launched a suicide mission and drove a Jeep Cherokee containing a bomb into Terminal One at Glasgow Airport.

Passengers were queuing just 20ft away but the device failed to go off properly.

Details of the plot emerged at the Old Bailey in London when Sabeel admitted withholding information about the terror campaign. Sabeel received a suicide e-mail from his brother along with orders to pretend he was in Iceland and to “keep him alive” for as long as possible to frustrate the police. 

The e-mail said: “Do not inform any one about me or my deed. It is about time we gave up our lives and our families for the sake of Islam to please Allah.”