Almost half of knifepoint robbery cases are closed in Suffolk because police cannot identify a suspect, figures have revealed.

Between 2017 and this March, 41% of investigations into 105 knife robberies were closed because no suspect could be identified.

In another 11%, the victim declined or was unable to support further action to identify a culprit.

Freedom of Information data showed five of the 12 knifepoint robberies investigated before April were closed through lack of an identifiable suspect, despite all victims supporting further action.

Police highlighted a number of reasons for the rate of closures and stressed cases never remained completely discontinued.

Detective chief inspector Jeff Yaxley said: "Discarding incidents where the victim knows the offender but won't name them for obvious reasons, like drug dealer on drug dealer robbery, you have to consider what a knife robbery looks like to put this into context.

"It can happen quickly, mainly during darkness, and be carried out by someone masking their face - all hampering the ability of a victim to recall a description.

"In that scenario, contact between offender and victim is small, unless there's a struggle, so forensic opportunities are limited, and it generally happens away from other witnesses or CCTV - all of which normally provide the building blocks of investigation.

"No witnesses and no forensics doesn't mean we just give up after basic enquires. We'll look at intelligence, previous offenders, where it happened, and sometimes a not brilliant description will give us at least half an idea.

"In Suffolk, the number of robberies is relatively low, but every single one goes to a trained detective within a CID team.

"Although investigations are called 'closed' on the computer, if something comes up later and it's worth chasing, we'll go after it."

From 22 police forces to provide comparable data, 42% of cases up to March 2019 were closed for want of a suspect. Since 2017, the national rate closed in the absence of a suspect was 55%, while 11% of victims did not support action.

Police Federation national vice-chairman, Ché Donald, said stretched forces were battling an "explosion" in violent crime.

More than 10,000 knives were seized and 1,372 suspects arrested in a week-long national Operation Sceptre crackdown in March.

The Home Office said £220m was being invested to steer young people away from crime.