Brar, who was on the hit list of Sikh militant groups, was on a private visit to London when he was viciously attacked on the evening of Sep 30. The retired general and his wife Meena returned to India Oct 3.
Three men and one woman were arrested "on suspicion of conspiracy to murder in connection with the investigation into the attempted murder" of Lt Gen Brar in central London Sep 30, Metropolitan Police stated.
A 33-year-old man and the woman were arrested in Wolverhampton Thursday evening. A third person, a 34-year-old man, was arrested after being stopped in a car on a street in West Bromwich. The fourth person nabbed is a 25-year-old man.
All four were taken to a central London police station.
The police had said that Brar "was assaulted with what is believed to be a knife or sharp weapon and suffered a wound on his neck".
"His wife was not injured in the attack," it added.
The attackers were "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", said an earlier appeal by the police.