THE government’s top law officer has failed in a bid to increase the jail term of a teaching assistant who secretly tried to produce handguns in a garden shed.

Tyrone Cox, who supervised young children at Montem Primary School, in Hornsey Road, Holloway, was jailed for 30 months at Wood Green Crown Court in May this year after admitting conspiracy to convert firearms and conspiracy to possess prohibited weapons.

But the Attorney General, Dominic Grieve QC MP, considered the sentences imposed on Cox, of Balmoral Road, Enfield, and his accomplice, Lewis Monk, were “unduly lenient” and referred their cases to the Court of Appeal for review.

Yesterday (Wednesday), three senior judges ruled the pair’s sentences, although merciful, were “not lenient enough” to now be increased.

Lord Justice Hughes told the court 26-year-old Cox, and Monk, 23, had bought four starting pistols from a sports shop in December 2006 and taken them back to a shed behind Monk’s mother’s house in Barclay Road, Edmonton.

Mrs Monk knew nothing of the plot, in which trained metal-worker Cox tried to convert to pistols into lethal weapons which could take bullets.

Police raided the shed before any of the weapons could be converted. Cox, who worked with three to five-year-olds by day, later admitted in interview that he had tried to make the guns to pay off a �200 debt to a drug dealer.

Monk was jailed for 25 months for his role in the plot after admitting the same offences as Cox.

Sarah Whitehouse, representing the Attorney General, told the court the minimum prison sentence for possession of prohibited weapons is normally five years and stiff penalties for gun offences are needed to deter others.

However, lawyers for Cox and Monk said the pair had clean criminal records and had not realised how much trouble the plot would land them in.

Lord Justice Hughes, sitting with Mr Justice Owen and Mrs Justice Thirwall, told the court the guns could have got into the hands of the drug dealers for use against innocent victims.

However, he said there was a “mismatch” between the serious crime and the “amateurish” criminals who carried it out.

He concluded: “These sentences, we think, were lenient and the judge did not, as he should have done, appreciate the balance between the public risk and the personal circumstances of the defendants.

“The question which is more difficult is, are the sentences so unduly lenient that it is necessary for this court to increase them, after the appellants have served a considerable part of their sentences.

“In these particular circumstances, we are convinced that it is not necessary and we therefore leave the sentences as they are.”