Met admits mistakes which could have stopped Harry Potter killer

A convicted knife thug who stabbed to death Harry Potter actor Rob Knox could have been arrested two months before but for missed chances by police officers, the Standard reveals this afternoon.

Karl Bishop, 21, was today found guilty of murdering the rising star outside the Metro Bar nightclub in Sidcup last May.

Rob's parents Colin, 55, and Sally, 50, burst into tears when the verdict was announced and were comforted by friends.

Bishop, armed with two large kitchen knives and his face "screwed up with rage", stabbed Rob five times when he went to his younger brother Jamie's aid. Five of their friends were stabbed in the 90-second melee.

Bishop had sought the confrontation because Rob, 18, a strapping 6ft 1in rugby player, had stood up to him the week before in a row over a mobile phone, the Old Bailey heard. Brian Altman, QC, prosecuting, said that Rob's life, full of promise, was brought to an end by a "habitual knife carrier" who thought of stabbing people as an "occupational hazard".

Today the Met admitted for the first time that Bishop was reported to police for an attempted knifepoint robbery two months earlier but detectives failed to arrest him.

Two weeks later the mother of the robbery victim also reported a burglary at her son's flat, and named Bishop as the suspect, repeating the accusation that her son had been threatened with a knife.

Scotland Yard admitted today that it had blundered in not arresting Bishop. The Met said it took the errors so seriously that it called in the Independent Police Complaints Commission to investigate.

As a result two police officers, a constable and a sergeant based in Plumstead, have been given written warnings.

The force said in a statement: "Lessons have been learned from what happened in this case and measures have been taken."

It also emerged this afternoon that Bishop was jailed for four years in 2005 for knifing two youths but was released early, in March 2007.

The police mistakes have similarities to those in the case of Peter Woodhams who was shot dead in Canning Town in August 2006.

He was attacked seven months before he died and gave police the name of his assailant — the same teenager who was convicted of his murder — but police failed to investigate properly.

The Old Bailey was told that Bishop had tried to cause trouble with Rob's friends before the fatal attack and had come off second best.

A week earlier he had limped away vowing revenge and warning "somebody is going to die", adding: "You don't know who you're messing with, I've put people down."

The following week Rob was celebrating at the Metro Bar after finishing filming Harry Potter And The Half Blood Prince. Bishop returned as promised, and was refused entry before ending up in a fresh confrontation with Rob and his friends after Jamie, 17, was threatened.

The knifeman was soon surrounded by a semi-circle of youths and Rob had to be held back as Bishop goaded them, shouting: "Who's going to make my f***ing day?" Rob was struck five times including one blow that severed an artery in his chest. He collapsed moaning "I've been stabbed, help me".

Bishop claimed he was acting in self defence but was found guilty of murder and will be sentenced to life tomorrow. Bishop was found guilty of wounding Rob's friend Dean Saunders, 23.

He was found guilty on majority verdicts of wounding with intent to cause grievous bodily harm to Charlie Grimley, 17, and 20-year-old Nicky Jones.

He was also found guilty by a majority of wounding Andrew Dormer, 17, but cleared of wounding another friend, Tom Hopkins, 19.