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
Rahman was ejected from his powerful job in April by an Election Commissioner after being accused of corrupt and illegal practices.
The service was due to start in September but there is no agreement on pay and conditions such as how many night shifts staff will work.
Would you know what to do if you needed help? Here's the official advice from the Foreign Office.