Two men have been found guilty of manslaughter after leaving a man to die in freezing waters in an unprovoked attack.

Despite heroic attempts by two passers-by to rescue him, the body of Ibrahim Ghrib, 20, was not recovered until the following morning.

Amran Chowdhury, 27, of Whitney Avenue, Ilford, and his brother Misba Chowdhury, 24, of the same address, were convicted at the Old Bailey yesterday.

Amran Chowdhury's then girlfriend, Steffi Rai, 27, of Holloway Circus, Queensway, Birmingham, was convicted of perverting the course of justice by helping him evade arrest.

A date for sentencing is to be confirmed.

Detective Constable Darrell Etchells, the investigating officer from the Homicide and Major Crime Command, said: "Today's convictions mark the end of a long and extensive investigation to bring to justice those responsible for Ibrahim's death.

"No motive has ever been discovered for the attack but I hope Ibrahim's family can find some peace in the fact that the jury are satisfied the Chowdhury brothers were responsible for his death."

The court heard that on the evening of Thursday March 18, 2010 the victim had been drinking with his 17-year-old girlfriend beside the water's edge in Garnet Street, Wapping.

Amran Chowdhury, who had also been drinking that day, was with his girlfriend inside a nearby block of flats, where she lived, overlooking Shadwell basin.

At around 9.25pm Amran Chowdhury left the premises, having made a short phone call to another man.

Minutes later he was joined in Garnet Street by several other men, including his brother.

This group of men, wearing hoods, then approached the victim and his girlfriend.

The man nearest Ibrahim's girlfriend snatched up a bottle they had been drinking from and suddenly hit her across the head with it, knocking her to the ground.

In her dazed state she became aware the group had surrounded Ibrahim, who was behind her near the water.

She grabbed the arm of one of the group and was hit again. She collapsed to the ground, briefly losing consciousness.

When she managed to get up she could hear Moroccan-born Ibrahim shouting from the 12-metre deep water. The group ran off.

Her screams alerted a passerby who tried to reach Ibrahim but was beaten by the freezing temperatures.

Another man, who heard noises from his flat overlooking the water, also raced to help. He jumped into the basin but again, was unable to help due to the cold.

The London Ambulance Service was called and paramedics and police attended.

Ibrahim's body was recovered the following morning by the Metropolitan Police's underwater search team.

The cause of death was given as drowning. Ibrahim also had some bruising but the autopsy couldn't determine if he had been pushed into the water or assaulted during the incident.

Amran Chowdhury's phone was also recovered from the scene.

A search warrant was executed at the then home of the Chowdhurys - Chamberlain House, Cable Street, Tower Hamlets, on March 19, 2010, and Misba Chowdhury was arrested.

His brother was not there but handed himself in at Limehouse police station three days later.

Rai was interviewed as a witness on April 23, 2010 and gave a detailed account of events that night, which were later proven to be false.

She denied knowing anything about Ibrahim's death - in fact she had witnessed what had happened from the third floor balcony of her home. She was arrested on May 25, 2010.

All three were released on bail pending further enquiries but there was insufficient evidence to charge at that time.

Following a review of the evidence, the CPS granted authority to charge in November 2013.