Five men who hoped to kill thousands of people with a vast fertiliser bomb were described by a judge yesterday as ruthless and devious misfits who had betrayed their country of birth.

Omar Khyam, the ringleader of the British terrorist cell, and his accomplices planned to use the 1,300lb (590kg) bomb on a target such as Bluewater shopping centre in Kent or the Ministry of Sound nightclub in London.

Jailing them all for life yesterday, Mr Justice Astill said that they were “cruel and ruthless misfits who should be removed from society for its own protection”.

The judge described Khyam, 25, as “ruthless, devious, artful and dangerous”. He gave warning that he and the others may never be released from prison. Khyam had spoken with “enthusiasm and pleasure of the slaughter of nonbelievers”, the judge said. “You took full advantage of the benefits free society had to offer. You exploited the freedoms you sought to destroy with such evil purpose. You betrayed the country that’s given you every advantage in life.”

Khyam will serve at least 20 years before being considered for parole, as will Waheed Mahmood, 35, and Anthony Garcia, 25, Khyam’s “personal assistant and close confidant”.

Jawad Akbar, 23, and Sala-huddin Amin, 32, will each serve at least 17½ years. All five were convicted of conspiracy to cause explosions. Both Khyam and Garcia were convicted of possessing fertiliser for the purposes of terrorism, for which they were given eight-year concurrent jail terms.

The two youngest defendants – Khyam’s brother, Shu-jah Mahmood, 20, and Nabeel Hussain, 22 – were each cleared of conspiracy and possession charges.

The judge said of the convicted men: “It may be that you consider yourselves heroes of the cause that you espouse. But you are considered by the vast majority of the population of whatever religious faith as nothing but cruel and ruthless misfits – and now you must pay the price exacted by that society.” He said that the “spiral of contamination” began with “the teachers and preachers of hatred and revenge who so often lurk in the shadows”.

Khyam, Waheed Mahmood, Garcia and Amin refused to enter court to be sentenced. Only Akbar, who had been found guilty by a 10-2 majority, sat in the dock to hear the comments of the judge.

The conspiracy that led to a jury deliberating for 27 days, the longest in British criminal trial history, had started in November 2003, with the purchase of the ammonium nitrate fertiliser that was central to the plot. The amount would have been capable of bringing down a large building.

When Garcia turned up at Bodle Brothers, the agricultural merchants, his request baffled John Stone, a salesman. Flashily dressed, he arrived in a customised Audi, with rap music blaring, and asked for the fertiliser for his allotment. It was winter, thought Mr Stone, and the order was enough to cover five football pitches. “What do you want all that for?” he asked. “Are you planning a bomb attack?” Unwittingly, he had hit upon the truth.

Months earlier, Garcia had been among a group that learnt about weapons and explosives in Pakistan. Two accomplices learnt how to prepare ricin. Garcia had taught the others how to dismantle and reassemble weapons. Under the leadership of Khyam they wanted to put their training into practice.

By now their conversations were being recorded by MI5. Operation Crevice involved every officer in the south of England and uncovered dozens of suspects across three continents. Members of the public had played their part when the fertiliser was taken to Access Storage, near Heathrow. Khyam refused to answer questions about why he was paying £207 a month to store £90 worth of fertiliser. Staff contacted police in February 2004, on the same day that Khyam collected Momin Khawaja, a Canadian expert in detonators, from Heathrow.

The pair were heard talking about remote-controlled devices and it was the involvement of Mr Khawaja that jolted MI5 into realising just how serious the scheme was becoming. The men went to a key meeting the next day in Craw-ley, which officers believe was also attended by Mohammad Sidique Khan, the ringleader of the July 7 bombers.

The fertiliser was switched by police for cat litter and five weeks passed before the gang were arrested. During this time they seemed “surveillance sensitive” – executing U-turns on the way to meetings, using multiple names and codewords, disposing of laptop computers and changing mobile phones.

Detectives acted when the conversation convinced them that the plot was slipping beyond their control. One suspect was recorded asking whether something was “ready to go”.

On March 30, 2004, officers from five forces arrested the seven defendants, who were charged with conspiring to cause an explosion likely to endanger life. Mr Khawaja was arrested in Canada and his trial begins imminently. Detectives found aluminium powder in a biscuit tin behind the shed at Khyam’s family home.

A week after their arrests, Mohammed Babar, an American al-Qaeda operative who trained with Khyam in Pakistan, was arrested in New York. He “crumbled”, pleaded guilty to terrorist offences and agreed to give evidence in return for immunity from prosecution for the fertiliser plot.

The intelligence service compiled a huge list of friends, relatives and contacts, many with multiple identities. Accomplices included “AD”, who was sectioned under the Mental Health Act but escaped from hospital. He was asked to carry out a suicide attack on the Tube but refused.

Two men from Luton – one who can be identified only as Q and the other who uses the name Abu Munthir – played pivotal roles in recruiting the Khyam cell. Both reported to al-Qaeda figures in Pakistan, including Abdul Hadi, who is being held at Guantanamo Bay.

Some of the defendants and associates worked at Gatwick and discussed its levels of security, leading surveillance officers to fear that the airport could be attacked.

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