"Have-a-go heroes" have been warned not to copy the example of a pensioner who tackled a gang of hammer-wielding robbers.
Ann Timson, 71, hit the gang of six with her handbag and forced them to give up their raid on a jewellery shop in Northampton.
She said: "I just kept swinging my bag, then they tried to escape. I landed several blows against one lad."
Northamptonshire Police advised people not to risk their safety but call 999.
Detective Inspector Ally White said: "We would like to thank all of the members of the public who assisted in the incident.
"However, we would always advise the public to call the police if they witness a crime, rather than risking their own safety by getting involved themselves."
Mrs Timson, a retired market trader, told The Sun newspaper: "My mother's instinct kicked in and I ran across the road shouting at the lads to stop it.
"Only then did I realise that they were smashing glass and that it was a raid."
In January 2010 the Metropolitan Police Commissioner, Sir Paul Stephenson, said people who put themselves in danger to tackle criminals should be celebrated as heroes.
He said such people "make our society worthwhile".
Earlier that month a 31-year-old builder, Sukhwinder Singh, was stabbed to death after he chased two men who had mugged a woman in Barking, east London.
His murder remains unsolved despite police offering a £20,000 reward last month.
A Victim Support spokesperson said: "It's not possible to tell people how to react in situations where others may be at risk, because they will inevitably follow their instincts.
"What the woman did was brave, but people also need to remember their own personal safety."
The Association of Chief Police Officers said they would defer to local forces for advice on "have-a-go heroes".
The Home Office, Ministry of Justice and Police Federation said they did not wish to comment on the case.
Four men from London, aged between 18 and 39, have been charged with robbery and vehicle offences and are appearing at Northampton Magistrates' Court.