The 17-year-old, who cannot be named for legal reasons, was sentenced to four months at a Young Offenders Institution last week.

But on Thursday he won an appeal at Ipswich Crown Court against that sentence. His barrister said the custodial sentence appeared to have been designed more as a deterrent to others rather than a punishment for what he had done.

Judge Peter Thompson, sitting with two magistrates, agreed that the teenager should not have been sent into custody.

He ordered that instead he should be the subject of a 12-month community rehabilitation order and must complete 100 hours unpaid work.

Nicola Furlong, appearing for the 17 year old, said that on the day he was sentenced by magistrates at Bury St Edmunds there had been four articles about youth knife and gun crime in a single national newspaper.

In the preceding week there had also been no fewer than nine television programmes on the same subject, she added, describing the coverage as a "media frenzy".

Appearing for the Crown Prosecution Service, John Fenn said the teenager had been stopped and searched in Mildenhall town centre shortly before 11pm on the evening of June 6.

He told officers that he had a knife tucked into his sock, held in place with a rubber band. It was found to be a nine-inch long kitchen knife with a five-inch blade.

"He said this was for protection 'because I got jumped by five Polish blokes'", Mr Fenn told the court. At Bury St Edmunds Youth Court he had pleaded guilty at the first opportunity to a charge of having a bladed article in a public place.

Miss Furlong said that a month before his arrest the teenager had been attacked by a group of five others. She said: "They were considerably bigger than him and he was very frightened. That is why he says he was carrying the knife".

The 17 year old, who is of slight build, had been fearful of what would happen if he had to face the same situation again.

"He says that he acted in genuine fear on that night. He had no intention to use it. He intended to show it to anyone who attacked him as a deterrent," said Miss Furlong.

Much of the TV and press coverage of knife and gun crime among young people at the same time as he was being sentenced related to gangs with which he had no association, she added.

Miss Furlong told the court: ""He has learned very much from this. He has some insight into his offending and fully understands that he should have not done what he did."