A 12 inch knife and quantity of benzodiazepines have been seized by the PSNI in Derry city centre.
The PSNI at Strand Road said they don't know what its officers might have prevented by seizing the large blade and 126 diazepam tablets this afternoon.
Police said officers from its Reducing Offending Unit saw two males acting suspiciously in the city centre and the items were recovered when they intervened.
One of the males is currently "assisting police with their enquiries".
"Police cannot always measure the impact of what they have prevented but they are glad in this case not to find out," the force said.