Moped-riding robbers threatened one of their victims with a hammer during a spate of thefts across north London.
Police have released CCTV images in the hope of catching four men who threatened a 57-year-old man with a hammer before demanding he hand over his watch and other items of jewellery.
The four men were on mopeds with false number plates and were dressed in boiler suits and motorcycle helmets.
The incident happened at approximately 6pm on April 11 in Platts Lane, but police are linking it to five similar offences which happened recently in the N2, NW2, NW11 and NW6 areas.
Police have increased patrols in these areas and are warning residents to call 999 immediately if they see anyone on mopeds acting suspiciously.