Police found this knife when they arrested a man on suspicion of robbery.
Officers were called to the Riversway area of Kings Lynn late last night.
They spoke with to 16-year-old boy who had been threatened with violence and had his bag taken from him. The victim's bag was recovered nearby.
A thorough area search was then conducted and at 23.45 hours on Gayton Road, a 25-year-old male was arrested on suspicion of robbery and he was found in possession of a knife.
A spokesman said: 'At the present time the male remains at King's Lynn Police Investigation Centre and the investigation continues.'
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