Eight anti-arms trade protesters accused of unlawfully disrupting an arms fair at the ExCeL should not have been acquitted, the High Court has ruled.

A judge at Stratford Magistrates’ Court cleared them in April 2016 after accepting their argument they had tried to prevent greater crimes, such as genocide and torture, by blocking a road to stop tanks and other armoured vehicles from arriving at the Defence & Security Equipment International (DSEI) exhibition in 2015 where they claimed illegal arms trading was taking place.

But now two High Court judges have ruled District Judge Angus Hamilton “misdirected himself in law” when he permitted the protesters to use the crime prevention defence under section 3 of the Criminal Law Act 1967.

Expert witness had told the judge there were historic breaches of UK arms exports controls at previous DSEI exhibitions.

Quashing the acquittals following an application by the Director of Public Prosecutions, Lord Justice Simon and Sir Kenneth Parker said the preventing crime defence was not relevant because there was no evidence that the commission of a crime was “imminent and immediate” at the time the eight chained themselves up outside the centre.

There was no evidence of any illegal arms trading at the 2015 exhibition but the protesters regarded it as reasonable to assume the level of illegal activity was similar to what had allegedly occurred at earlier events, said Lord Justice Simon.

The court decided not to order a retrial, saying it was not necessary in the “overall interests of justice” for several reasons, including the eight were of previous good character.

Isa Al-Aali, from Bahrain; Lisa Butler, Angela Ditchfield, Thomas Franklin and Susannah Mengesha, all from the UK; Javier Garate Neidhart, from Chile; Luis Tinoco Torrejon, from Peru, and Bram Vranken, from Belgium, had all denied wilful obstruction of the highway.

After the High Court ruling in London, they said they remained “wholeheartedly unrepentant” for their actions.

A group statement said: “We cannot rely on the Theresa Mays and Donald Trumps of this world, whose idea of keeping us safe and promoting human rights abroad is to arm despotic terroristic head-chopping regimes such as Saudi to the teeth.”