A man with a 'troubled background' who ended up homeless in London has been given a two-year sentence after coming to Norwich to sell cocaine.

Sean Amon was 17 when he was snared by the undercover police operation codenamed Granary, which led to more than 100 arrests and the disruption of multiple county lines dealer groups.

Amon had been tasked to deal to the undercover officer known as Tommo on December 12, 2017, and sold him a single wrap of "pure cocaine" for £20.

"Tommo obtained a phone number on December 12 and he spoke to a male with a London accent," prosecutor Chris Youell told Norwich Crown Court on Friday.

"At 3.20pm he saw Mr Amon walking towards him from the Drayton Road stores, and nodded to him.

"Tommo took that as an indication a deal was about to take place. They went to the rear of the post office and Mr Amon went into a garden and dealt drugs to Tommo for £20."

The exchange was recorded by officers supporting Tommo, and Amon's DNA was found on the wrap of cocaine.

"Because of the large number of arrests that had to be made they could not all be made at once," said Mr Youell, adding that he was eventually arrested in Croydon on March 26.

Daniello O'Donovan, for Amon, said the offence was almost two years ago, when he would have been 17.

"He became involved because of his extremely difficult mental health circumstances," she said.

"He is a young man who lived with his mother and stepfather. The stepfather very much took against him and made it plain he was leaving the home when he was 16 years old. There were no prospects for him and he was, to all intents and purposes, homeless."

Judge Anthony Bate told Amon: "You have a troubled personal background and not the strongest of family ties.

"Your involvement in this offence was when you were 17 and then of good character.

"Since then it is sad to see you have committed other offences. It is up to you ultimately to take advantage of the support available to you and lead an honest and productive life on your release."

Amon, of Gillett Road, Thornton Heath, Croydon, admitted supplying crack cocaine and failing to surrender.

He was sentenced to two years in a young offenders' institution.