The 15-year-old is still being held in juvenile detention and appeared in Armidale Children's Court where he pleaded guilty to one count of robbery armed with an offensive weapon.

The teenage boy was armed with a knife when he entered the BP service station, on the corner of Marsh and Dumaresq Streets, about 2pm on July 23.

Once inside, he confronted the attendant, and threatened him, demanding cash.

Anti-counter jumping security wiring prevented the teenager from getting any closer to the employee, who retreated to a secure area, police said at the time.

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The teenager then stole lollies and drinks and fled the scene.

Detectives investigating the robbery homed in on the teenager less than 24 hours after the offence. He was arrested at 8am the following day at an Armidale home and taken to Armidale Police Station where he was questioned and charged.

He's been in custody since his arrest.

The court accepted the guilty plea and adjourned the case for sentencing in September before the magistrate.

The teenager made no application for bail and it was formally refused.

A second man remains before the court in connection to the robbery.

Angus Morris is accused of being an accessory to the hold-up before it happened, and was arrested on July 24 in Barney Street.

Detectives allege Morris knew the robbery was going to occur and aided the teenager before the offence.

Morris, 23, was also wanted by police after allegedly stealing $400 from the catholic church, earlier that week.

He has not been required to enter pleas to the accessory to robbery offence or larceny

It was witness statements along with security surveillance footage which also connects him to the robbery, detectives claim.

He was refused bail earlier this month in Armidale Local Court and will return to court in October.

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