They slipped past security guards, ran across a frosted runway to the hangar containing Hawk jet number ZH 955 and forced open the door. Then, using household hammers, they smashed the pounds 12m plane's sophisticated electronics.
When they had finished, they say, they tried to attract the attention of a passing patrol car and danced in a circle before closed-circuit televison cameras. Eventually, despairing of the on-the-spot security operation, they used a BAe phone in the hangar to contact the Press Association news agency in London and ask a journalist there to inform the BAe management of what they had done.
By the time security guards arrived at the scene, at 5am, the intruders had been in the factory for more than two hours and had caused, it is alleged, damage to the aircraft to the tune of pounds 1.7m.
This week the three women will appear in Liverpool Crown Court charged with causing, and conspiring to cause, criminal damage. Accused of conspiracy with them is Angie Zelter, who was arrested a week later after announcing she was going to the factory to continue the damage her friends had started. If convicted they could be sentenced to up to 10 years in prison.
Why did they do it? Because, they say, they were determined to prevent the plane from reaching its purchasers, the Indonesian government, in case it was then used against the people of East Timor.
East Timor is a long way from Lancashire. A small former Portuguese colony, it was forcibly annexed by Indonesia in 1975 and since then its people have suffered the most brutal persecution. Amnesty International estimates that no fewer than 200,000 people - a third of its present population - have been killed.
The four women hope their case will highlight the plight of the Timorese and draw attention to the conflict between human rights and the arms trade.
And whatever the outcome, the Warton story demonstrates a remarkable globalisation of such issues, when people in one of Europe's most deprived areas, Merseyside, can become so involved with the fate of a tiny, underdeveloped country on the far side of the world.
The defendants say they do not intend to deny that they took part in the break-in or caused the damage at Warton, but have said they will plead not guilty and will argue, among other things, that what they did in damaging the aircraft was not a crime but an attempt to prevent a greater crime.
"I've never doubted it was the right thing to do, even in my darkest hours when I've felt I don't want to be in prison," said Andrea Needham, interviewed awaiting trial in Risley prison in Cheshire, where all four have been held. She added: "It was such an amazing feeling dancing in the night outside a hangar where we had disarmed the plane."
Joanna Wilson explained: "We are pleading not guilty on the basis that we had lawful excuse as we were acting to prevent British Aerospace and the British Government from aiding and abetting genocide."
The focus of their concern is a pounds 500m arms contract that Britain signed with the Indonesian government in 1993, involving the sale of 24 British Aerospace Hawks. The sale was presented in Britain as excellent news for the defence industry, which has shrunk by 100,000 jobs in the past 15 years and is still contracting; the women argue that the deal is extremely bad news for East Timor.
They call themselves the Ploughshares Four - they belong to the Ploughshares Movement, a Christian peace group founded in the United States during the Vietnam War, drawing its name from the Old Testament words: "They shall beat their swords into ploughshares."
The four come from different walks of life and different parts of the country. They do not share a religion, but they say they have been influenced by work they have done in caring professions.
Their interest in East Timor has developed since they saw news reports and televison footage of a massacre there in 1991. Indonesian troops opened fire on a peaceful demonstration in Santa Cruz, killing 271 men, women and children, many of them trapped in a graveyard as they fled the shooting. The news of the massacre provoked international outrage and condemnation, and when the British Hawk contract was signed less than two years later, the women were appalled.
An element of their defence, they say, will be the presentation of evidence that the Hawks, which both the Indonesian and British governments assert are merely training aircraft, are earmarked for a wider role.
They are likely to cite evidence which has already appeared in the press: BAe's own sales video for the Hawk, for example, boasts of the plane's "significant ground attack capabilities", and in the lead-up to the deal an Indonesian Air Marshal said the jets "will be used not only to train pilots but for ground attack". Last year this newspaper reported that Hawks, presumably from a previous batch of 20 planes sold to Indonesia in the 1980s, had been seen flying over Dili, the East Timor capital.
Joanna Wilson has said that that report, describing two of the planes passing side by side over the town on 10 November, the eve of the fourth anniversary of the Santa Cruz massacre, gave added urgency to their actions.
The four insist that there is nothing remarkable about them, or what they have done. "We aren't super heroes," said Andrea Needham. "We are four ordinary women. Anyone could do what we have done if they feel strongly enough about what is happening." They demand to be seen as strictly of equal rank; none leading, none lagging.
Nor are they the first to fight such a case. In 1993 Chris Cole, another Ploughshare member, caused damage to the tune of pounds 90,000 to aircraft at BAe's Stevenage plant. He later argued in court, as the women are expected to, that he was acting with reasonable force to prevent a crime - namely genocide in East Timor. A first trial resulted in a hung jury; at a second, he was sentenced to eight months' imprisonment.
Unremarkable as they profess to be, these four women have stirred some strong support, especially on Merseyside. In Kirkby, where Joanna Wilson, 32, is a tutor in further education and an Independent borough councillor, a wide support network of residents' associations, environmental groups and churches has continued her campaign for East Timor since her arrest.
Although Kirkby is one of Britain's poorest towns, a stroll round the pedestrian precinct revealed that even before the trial many passers- by knew about the affair, even if they were not too sure where to place East Timor on the map.
Keith Hassell, chairman of a residents' and shopkeepers' association, said even children on the estates knew about the case, and about East Timor. When they are not arguing about sport, he said, "there's a good chance they'll be going on about this tiny tropical island thousands of miles away where people are being killed by the government and the army. And Britain is selling them weapons by the lorry-load. How do you explain that to your kids?"
The four who will appear in court on Tuesday make a disparate group. Besides Joanna Wilson, Angie Zelter, at 45, is the eldest. A widow, she lives in East Runton on Norfolk's north coast.She is a Green Party member and used to work at an environmental agency in Norwich.
Andrea Needham, 30, comes from Suffolk but has been living in Kirkby. She trained in Newcastle as a physiotherapist and practised for a time in Orkney before going to Washington. A Roman Catholic convert, she was attracted to Ploughshares there after working with a Catholic group looking after the homeless. Lotta Kronlid, at 28 the youngest, is Swedish, and grew up near the southern city of Gothenberg. She has worked most recently as a gardener and cleaner living in Oxford.Reuse content