LONDON: Two British hitmen who went to the wrong address and stabbed an innocent teenager to death were jailed for life on Friday.

Ben Hope, 39, and Jason Richards, 38, were both heroin addicts who were paid £1,000 ($1,600, 1,100 euros) each to murder a middle-aged family man who owed money to a shady businessman in Cardiff.

But the pair -- high on drugs and wearing balaclavas -- went to the wrong house in the Welsh capital and murdered 17-year-old Aamir Siddiqi by mistake.

The schoolboy was brutally knifed to death on the doorstep of his home on April 11, 2010. Hope and Richards also stabbed Aamir's parents, Iqbal and Parveen, as they fought to save their son.

Aamir had been waiting for his Koran teacher and had rushed past his parents when the doorbell rang, answering the door to his killers.

Hope and Richards both pleaded innocence during their four-and-a-half month trial at Swansea Crown Court in south Wales, but a jury unanimously found them guilty of Aamir's murder as well as the attempted murder of his parents.

Judge John Royce told the hitmen that they were likely to die behind bars as he handed them life sentences with a minimum term of 40 years each.

"Your attack on him was brutal, savage, callous and cruel," Royce told the pair.

"You hacked him to death in front of his parents, who fought in vain to save Aamir."

Royce added: "If you die in jail, few will shed a tear and many will say it will be more than deserved."

The judge described Aamir as a "bright, gentle and courteous boy who was much loved by his family".

He had secured a place at Cardiff University to study law and had a future "brimming with promise", Royce said.