Police are re-examining more than 100 murders in England and Wales they suspect could be so-called honour killings, it has emerged.
A taskforce to examine 'honour killings' was launched last year
Scotland Yard detectives are examining murder files going back 10 years - 52 in the London area and 65 in other parts of England and Wales.
Many of the female victims were from South Asian communities.
Detectives are not reopening the cases but hope to learn more about the scale and nature of the phenomenon.
The Metropolitan Police will give details of its inquiry at a conference in The Hague on Tuesday.
As well as South Asian communities, some of the victims came from Arabic or eastern European backgrounds.
Motives for the murders often included relationships which the families felt brought them dishonour.
Police say some of the murders were carried out by contract killers hired by the families.
They also believe that so-called "bounty hunters" were involved - people, including women, who make a business out of tracking down victims.
Commander Andy Baker, head of the Metropolitan Police's Serious Crime Directorate and the chairman of the new strategic taskforce, hopes the review will help future investigations.
He said: "We are not re-opening these cases - many of them have been through the courts with convictions.
"It is a matter of looking at these cases and learning how we can prevent killings in the future."
Monday's conference, hosted by Europol, is intended to raise awareness about this type of crime and share ways of tackling it across Europe.
Last September the Met announced new research into the culture surrounding "honour killings".
The undertaking followed the conviction of Abdalla Yones, a Kurdish Muslim, for the murder of his 16-year-old daughter Heshu after she formed a relationship with a man of whom he disapproved.
At the time, Commander Baker said the force needed to understand the culture surrounding "honour killings".
He said: "We've been unaware, we've been ignorant of the crimes going on."
The re-examination of past cases has been welcomed by members of communities often affected by the murders.
Diana Nammi, director of the International Campaign Against Honour Killing, said: "I believe these killings are more widespread than official figures suggest.
"We need to stop these murders and this move by the police is very positive."
Ram Gidoomal, of the South Asian Development Partnership, called for police to work alongside social services to prevent killings.
He told BBC Radio 4's Today programme: "I would like to see what action has been taken already - it is not as if we have just been made aware of this issue.
"Everyone needs to be educated to look out for early warning singles. All agencies need to share information."