A woman from Croydon, south London, has been found guilty of assault after she abused a lesbian couple within earshot of school children and stuck her finger up another woman’s nose.

Diana Marquis, 51, a resident of Wandle Housing Association, pleaded not guilty to two counts of assault, one of harassment, and three counts of threatening behaviour over a series of incidents in June 2012.

This week Croydon Magistrates’ Court found her guilty and ordered her to attend diversity awareness classes and perform 200 hours of community service, on top of paying £100 to each of the victims.

Marquis was convicted of assaulting Isobel Hodson and directing homophobic slurs at her and her partner, Stephanie Richards, calling them “dirty lesbians” in the playground of West Thornton Academy School.

Children aged between 5 and 11 witnessed the row. Marquis threatened head teacher Jo Simmonds, saying: “I’m gonna take that smile off your face.”

When the couple’s friend Debbie Cooplestone tried to intervene, Marquis assaulted her. The court heard that “the assault involved the defendant sticking her right index finger in her [victim's] right nostril, causing her discomfort.”

Marquis told a teaching assistant “I will kill everyone. I will go to prison for my children. I will protect my children.”

Before the incident Marquis had verbally abused the couple on four other occasions between 13-20 June.

She had been angry about the school’s management of a fight between her son and the couple’s daughter.

After the assault the parties left the scene, but returned for mediation talks. These quickly went downhill when Marquis swore at the couple and spat in Ms Hodson’s face.

“Ms Richards admits she attempted to punch the defendant, but she ducked out of the way,” the court heard.

In 2009, Marquis appeared in Inside Housing magazine, speaking about her participation as a former volunteer antisocial behaviour mediator she said: “We started training last September, doing 40 hours over 10 weeks. We took part in group sessions, discussions and role playing. We looked at anger management and non-violent communication.

“I’ve found it very useful. I didn’t know what to expect but it opened my mind. It taught me to see both sides of an argument, even with my own children.”

Marquis has not undertaken any further training for the past few years.