THE Ministry of Defence (MoD) will today challenge an inquest's ruling that a young North-East serviceman was unlawfully killed during a chemical weapon test more than 50 years ago.

Leading Aircraftsman Ronald Maddison, from Consett, County Durham, died aged 20 after having droplets of deadly sarin dabbed on to his arm at the Porton Down chemical warfare testing facility on Salisbury Plain, Wiltshire, in 1953.

Winston Churchill's Government ordered that the initial inquest, which reached a verdict of misadventure, should be held in secret for reasons of "national security''.

But after years of campaigning by Mr Maddison's family, an inquiry was launched by Wiltshire Police in 1999.

In 2002, Lord Chief Justice Lord Woolf granted permission for a second inquest to be held and a coroner's jury returned a verdict of unlawful killing two years later.

The ruling paved the way for Mr Maddison's family and those of other servicemen who were human guinea pigs to seek compensation from the Government.

Today, the MoD will challenge that verdict at a hearing of the High Court, in London, before Lord Justice Richards and Mr Justice David Clarke.

It will argue that Coroner David Masters was "wrong in law'' to leave a verdict of unlawful killing open to the jury.

When it became known that the MoD intended to seek a judicial review - despite admissions that there had been negligence - armed services veterans responded with a barrage of criticism.

The High Court has already ordered the coroner to authorise disclosure of tapes made of his summing up and the directions he gave to the jury.

The MoD won leave to challenge the decision after a High Court hearing last April.

Judge Mr Justice Collins said he was giving no view on whether or not the MoD's challenge would eventually succeed, but he left it open to Mr Maddison's family to argue that the bid to over- turn the verdict should be halted.

Nick Brown, representing Mr Maddison's sister, Lilias Craik, and other members of his family, were given a month to submit full written arguments in support of the jury's verdict.