Anyone who feels they know who it is should phone 101 or the Crimestoppers charity line anonymously on 0800 555 111
He says: "I'm going to leave you here, I'm going to take your wife (unintelligible). "You can ring the police in two minutes, we'll be round the corner." Police say they hope someone will recognise the distinctive accent.
More top news
Decontamination work is to begin at nine sites across the city.
Philippa has Friday's weather for the east
Philippa has Friday's weather for the west