Stating that detectives were keeping an open mind on the motivation behind the attack, the police said in a statement yesterday that they were particularly keen to speak to people who assisted Brar and his wife after the attack on Old Quebec Street in central London.

No arrests had been made until last night, the police said.

"The four men are described as wearing dark clothing and long black jackets. They all had long beards. One of the men is described as younger and slimmer than the other three. They all fled in the direction of Oxford Street," the statement said.

"Detectives are keen to speak to anyone who was in the area at the time or who may have information about the incident. In particular they want to speak to those people who assisted the wife and the victim at the scene following the attack," it added.

According to Brar, a mobile phone had been recovered from the scene, which may help lead the police to the assailants. The police were also expected to go through CCTV footage from the area that has several cameras.

More than 28 years after he led Operation Bluestar to flush out insurgents from the Golden Temple in Amritsar, Brar was injured in a knife attack by unidentified men in London on Sunday night.

London police sources said two persons had been detained in connection with the attack in which Brar’s wife was also injured as she was pushed to the ground. Brar, 78, was discharged from hospital on Monday evening and the Indian high commission is helping the couple return to India at the earliest, officials said.

Central intelligence sources said Brar was visiting his daughter in Britain and was walking back to his hotel in Mayfair in Central London with his wife around 10 pm when four men attacked him. He was struck on the neck and the attackers fled when his wife raised an alarm.