Protesters taken to court after preventing a deportation flight from taking off from Stansted Airport have had their convictions overturned by the Court of Appeal.

The so-called “Stansted 15” cut through the Essex airport’s perimeter fence in March 2017 and locked themselves together around a Boeing 767 jet chartered by the Home Office to transport people from UK detention centres for repatriation to Africa.

They were convicted at Chelmsford Crown Court in December 2018 of the intentional disruption of services at an aerodrome under the Aviation and Maritime Security Act 1990 (Amsa) – and the following February three were given suspended jail sentences and the others handed community orders.

But in a judgment published on Friday, the Lord Chief Justice, Lord Burnett, sitting with Mr Justice Jay and Mrs Justice Whipple, overturned their convictions.

They ruled that the protesters should not have been prosecuted for the “extremely serious offence” they were charged with under Amsa “because their conduct did not satisfy the various elements of the offence”.

“There was, in truth, no case to answer,” the judgment said.

“We recognise that the various summary-only offences with which the appellants were originally charged, if proved, might well not reflect the gravity of their actions.

“That, however, does not allow the use of an offence which aims at conduct of a different nature.”

“All the appellants’ convictions must be quashed,” the judges added.

In a statement on behalf of the protesters, May McKeith said the “nightmare” of the “bogus charge”, trial, and threat of a prison sentence had dominated the activists’ lives for four years, adding “despite the draconian response we know our actions were justified”.

The Stansted 15 were granted permission to appeal against their convictions in August 2019 and, at a three-day hearing in November, lawyers for the activists told the court that the legislation used to convict the 15 is rarely used and not intended for this type of case.

In documents before the court, the Stansted 15’s barristers argued that the Amsa law is intended to deal with violence of the “utmost seriousness”, such as terrorism, not demonstrators.

In the judgment, Lord Burnett said it could not be established on the evidence in the case that the group’s actions created disruption which was “likely to endanger” the safe operation of the airport or the safety of people there.

He said: “Taking the Crown’s case at its highest, and considering all relevant potential consequences, it could not be established to the criminal standard that the actions of the appellants created disruption to the services of Stansted airport which was likely to endanger its safe operation or the safety of persons there.”

At November’s hearing, the Stansted 15’s legal team argued that Amsa is not concerned with risks of “a health and safety-type nature” posed by those who have trespassed at an airport without causing or intending to pose “a direct risk of endangerment” to the operation of the airport, or people there.

In written submissions, they argued that, instead, the law relates to “an offence of unlawful violence of the utmost seriousness, directed at individuals who intentionally and unlawfully deploy offensive devices, substances and/or weapons, intending by that deployment to disrupt airport services in such a way as to endanger or to be likely to endanger the safe operation of the airport as a whole or the safety of the body of persons at such airport.”

Barristers representing the Crown said the convictions were safe, with Tony Badenoch QC telling the court: “We don’t accept that the Act is constrained to terrorism and nothing else.”

Other arguments put forward by the protesters’ lawyers – including that there were errors in directions given to the jury, and defences the group wanted to rely should not be have been withdrawn from the jury – were dismissed by the Court of Appeal.

In her statement, Ms McKeith said: “It is painful for it to be finally acknowledged that the past four years’ of prosecution should never have happened.

“But for many people caught up in the UK immigration system the ordeal lasts much, much longer.

“In the middle of a global pandemic the Government is still locking people in detention centres and brutally forcing people onto secret night flights, often to places they don’t know.

“The nightmare of this bogus charge, a 10-week trial and the threat of prison has dominated our lives for four years.

“Despite the draconian response we know our actions were justified.

“Eleven people, including survivors of trafficking, who would have been deported that night are still in the UK.

“Mothers, fathers, colleagues, friends and family members are rebuilding lives the Government attempted to destroy.”

A Crown Prosecution Service spokesperson said: “We will consider the judgment carefully in the next 28 days”.

A Home Office spokesperson said: “The decision of the Court of Appeal centred on the offence for which the individuals were prosecuted and should not be viewed as condoning their behaviour nor the disruption they caused.

“We will continue to work with the police to respond robustly to any future activity which attempts to frustrate or disrupt charter flight operations.”

The 15 are: Helen Brewer, 31; Lyndsay Burtonshaw, 30; Nathan Clack, 32; Laura Clayson, 30; Melanie Evans, 37; Joseph McGahan, 37; Benjamin Smoke, 21; Jyotsna Ram, 35; Nicholas Sigsworth, 31; Melanie Strickland, 37; Alistair Tamlit, 32; Edward Thacker, 31; Emma Hughes, 40; May McKeith, 35; and Ruth Potts, 46.