Dr Imran Farooq was on his way home from work when he was attacked outside his home in Green Lane, Edgware shortly before 5.30pm on Thursday 16th September 2010.
A post-mortem gave his cause of death as multiple stab wounds and blunt trauma to the head.
A five and a half inch-bladed kitchen knife and a house brick used in the attack were recovered at the scene.
Detectives from the Met Police Counter Terrorism Command remain committed to finding those responsible.
They believe his murder would have required careful planning and would have required help from other people, some of whom may have provided assistance or information unwittingly.
They want to speak to anyone who was asked for information about Dr Farooq and his routine.
More top news
Black Friday could kick off the biggest ever weekend of shopping in the UK with bargain hunters predicted to spend almost £8 billion.
A commuter is on track to get married after using the information screen at Waterloo station to pop the question.
Parents of an apprentice carpenter who was stabbed to death fear knife crime is "out of control" in the capital.