A man brandished an iron bar and assaulted staff during an attempted robbery in Watford Costcutter.
The man, described as white and aged between 20 and 30, entered the store in Orbital Crescent at around 6.20am on Friday, June 20.
He approached a memeber of staff and a brief struggle followed.
No items were stolen from the store and the iron bar has been recovered by the police.
The man then left the store and got into a green X-plated Toyota Yaris. This vehicle was later found abandoned in Harris Road. The driver was seen to run in the direction of Summerfield Road.
Detective Sergeant Ian Siggery is investigating the incident, and said: "Thankfully the member of staff was not seriously injured but was understandably left shaken by what happened.
"We would like to hear from anyone who remembers seeing a green Toyota Yaris being parked or driven around the area in the days leading up to this incident. If anyone remembers seeing this or anyone or anything else unusual or suspicious, they should contact me immediately."
Anyone with information is asked to contact DS Siggery via Hertfordshire Constabulary’s non-emergency number 101, citing crime reference C4/14/1228. Alternatively, Crimestoppers anonymously on 0800 555 111.