Police have produced a second edition of a ‘cold case calendar’ that they hope will encourage prisoners to pass on information about unsolved crimes.

The first edition was trialled in five jails at the start of last year and rolled out across the whole country in July when it proved a success. Each weekly page features a description of a major crime along with an appeal to contact police with information in five languages including English, Russian and Arabic.

Police said last year’s calendar produced 78 tips, 32 of which were useful. Nine of the 52 cases featured were reopened during the course of the year, seven of them as a result of tip-offs.

This year’s calendar features 43 murders or suspicious deaths, eight missing persons cases and one robbery, police spokesman Jeroen Hammer told NOS. ‘They are all very serious crimes that so far have not been solved.’

In total around 1,500 murders in the Netherlands remain unsolved. Research by police last year indicated that around 800 people in the country have information about killings that they have never disclosed.