LONDON – Five al-Qaida-linked men were sentenced to life in prison Monday for plotting to bomb a nightclub, power plants and a company doing work in Iraq, a plan that exposed links between their terror cell and the suicide bombers who attacked London’s transit system in 2005.

The five, all British citizens, were convicted Monday of plotting to attack the London targets with bombs made from a half-ton stockpile of fertilizer after a yearlong trial in which prosecutors and an FBI informant claimed the group was linked to al-Qaida leaders. It was Britain’s longest terror case.

Surveillance teams tracking the five men stumbled onto the transit attackers over a year before they killed 52 commuters on July 7, 2005, but officials failed to piece together intelligence in time to halt the blasts.

Though agents slipped a tracking device on transit bombing ringleader Mohammed Siddique Khan’s car and heard him pledge to carry out violence against non-Muslims during bugged conversations, Britain’s MI5 spy agency halted surveillance, deciding he was not a priority.

Details of ties between the plotters and the subway bombers were kept secret from the jury to ensure a fair trial. The links were revealed in closed sessions and confirmed Monday by government officials and police.

Security officers claim Khan, accomplice Shehzad Tanweer and the mastermind of the fertilizer bomb plot, Omar Khyam, trained together at camps in Pakistan and met Abdul al-Hadi al-Iraqi, an al-Qaida operative now held at the U.S. prison camp at Guantanamo Bay.

The revelations are at odds with statements by Britain’s government after the 2005 attack, when senior ministers said the strike was unexpected and the perpetrators unknown.

Jurors deliberated for almost a month over the plot to detonate bombs made from 1,300 pounds of fertilizer stockpiled in a London storage unit.

Khyam, 25, Anthony Garcia, 25, Jawad Akbar, 23, Waheed Mahmood, 35, and Salahuddin Amin, 32, were sentenced to life in prison for conspiring to cause explosions.

Garcia, Khyam and Waheed Mahmood will be eligible for parole after 20 years, and Amin and Akbar, after 17 1/2 years, but all five were warned they could face spending the rest of their lives in jail.

Two others, Nabeel Hussain and Shujah Mahmood, were cleared of conspiracy to cause explosions. All seven are British citizens, six with family ties to Pakistan.

“The security service will never have the capacity to investigate everyone who appears on the periphery of every operation,” MI5 chief Jonathan Evans said, adding his agents would always regret failing to halt the London bombings.