The ringleader of a girl gang who robbed two other teenagers at knifepoint has been locked up for 18 months.

Natalie Hughes, of Woodmans Road, Chipping Sodbury, led a gang who robbed Laura Coles and Kirsten McCann of their handbags and contents in the grounds of Gloucester Cathedral in July.

Yesterday 18-year-old Hughes and co-defendants Martha Brown, 18, of Stroud and a 15-year-old Gloucester girl, who cannot be named for legal reasons, all admitted robbery.

Crown prosecutor Lisa Hennessy said that at 10.40am that day Miss Coles and Miss McCann were in the cathedral grounds when the gang approached and one demanded £2.

When the pair refused Hughes said: "Shall we give them a permanent smile?" – a reference to cutting their mouths.

The court heard Hughes punched Miss Coles in the jaw and held a knife to her stomach before both victims were robbed.

Mrs Hennessy said the trio worked as a gang, they were all involved and it was a planned attack.

Hughes had no previous convictions but had been reprimanded for shoplifting and warned for an assault.

Brown also had no previous convictions but had a shoplifting reprimand and warning for assault in June this year.

The juvenile had previous convictions for battery and criminal damage, the court heard.

Carol Knotts, representing Hughes, said: "She has realised what she did was wholly unacceptable," said Ms Knotts, adding that she would like to "turn the clock back".

She said Hughes was using drugs at the time of the incident but had now moved away from her former associates.

Steve Young, for Brown, who was 17 at the time of the robbery, said she had not made any threats or made any physical contact. She was at a low point in her life having suffered a miscarriage, said Mr Young.

Dermot Clarke, for the 15-year-old, said she had been on the periphery and had expressed remorse.

Hughes was sentenced her 18 months' detention in a Young Offenders' Institution.

Brown was given an 11-month suspended sentence with supervision for two years and 20 hours of community activity. The 15-year-old girl received a two-year supervision order with a six-month 9pm to 6am curfew and must wear a tag.