The hooded gang attacked Premier store owner Guljinder Hayer of Worle, Somerset, after he refused to hand over money from the till. But assistant Ann Withers beat them back with a plastic broom and chased them outside.
The story broke as a new law to better protect 'have-a-go-heroes' came into force. It gives business owners a legal right to defend themselves against burglars and muggers without fear of prosecution.
Police and prosecutors will now have to assess a person's actions based on their situation "as they saw it at the time", even if in hindsight it could be that unreasonable force was used.