A SPATE of knife murders over the past 15 months have cost £100million in police investigations, a Sun on Sunday probe reveals.

Since the beginning of January 2018, there have been 99 knife murders in London.

That means each investigation and subsequent trial costs an average of just over £1million.

Campaigners said it showed money should be spent on preventing crimes through more police and better community ties. The starting salary of a police officer in the capital is £22,344, and the average pay of a London youth worker is £20,282.

The total £100million investigations cost could pay for 4,475 police constables or 4,930 youth workers a year.

Det Chief Supt Richard Wood, head of Scotland Yard’s homicide command, said: “There’s no such thing as a typical murder. You could have a domestic where the suspect is found with the knife in their hand which would not cost £1million, or a complicated gangland killing where you have numerous suspects.”

Tony Blockley, a former detective chief superintendent, said: “Even a non-complicated investigation can cost £500,000.”

And Patrick Green, CEO of the Ben Kinsella Trust, said he felt that “£1million per investigation is a conservative estimate”.

Across Britain, there have been 49 knife killings this year — so a quarter of the way through 2019 the bill is approaching £50million.