The Real IRA unit responsible for killing a workman was under close surveillance in the days leading up to the attack, Seán Hartnett has claimed.
David Caldwell was killed after he picked up a bomb concealed in a lunch box at a Territorial Army base in Derry in August 2002.
A former UDR member who left the regiment in 1985, he had been carrying out construction work at the unmanned site.
In his book Hartnett reveals that in the days leading up to the deadly attack several key members of the Real IRA unit were being monitored by his unit.
He also reveals the extraordinary lengths authorities were willing to go to monitor the movements of republican suspects.
Despite near blanket surveillance, members of the bomb team managed to give undercover British soldiers the slip and transport the deadly device from the Republic to its target.
Hartnett reveals previously unknown details about the attack and how authorities came within a whisker of stopping it.
The account also reveals some of the tactics authorities go to in their undercover war with republicans.
He reveals that a key suspect based in Strabane, who had links to the Provisional IRA, was given special ‘Charlie One’ status by undercover soldiers.
The term Charlie One - which gives the book its title - was used to describe the primary surveillance target during undercover operations.
Hartnett reveals that the operation centred on a Strabane-Derry based Real IRA cell and a white Vauxhall Cavalier and was based on information gathered using electronic intelligence techniques.
He said that the military were aware that the car was to be used to transport a bomb, however the “where and when were unknown”.
He reveals how his unit removed the car from the front of a suspect’s house in Derry before fitting a tracking device and later returning the vehicle.
“At about 0300, with the streets of Derry entirely dead, in one smooth, flowing movement of operators dressed in normal civilian clothing, and communicating with just clicks on the radio network, one white Vauxhall Cavalier parked on a driveway in Derry was unlocked, opened and rolled silently away while another was rolled into its place.
“Within an hour the dance was repeated and we all went home to bed.”
Hartnett reveals that the suspects were tailed 24 hours a day by British soldiers working in shifts.
Often the number plates and vehicles had to be changed over concerns they had fallen under suspicion form republicans, who often deployed their own counter-surveillance measures.
According the author the suspect car was even transported across the border in a bid to evade detection.
Hartnett says that two days before Mr Caldwell was killed the white Cavalier returned to Derry before meeting with another vehicle.
He says the cars parked boot to boot before driving in different directions with Charlie One travelling in the other vehicle.
Forced to make a crucial decision the officer in charge of the operation decided to continue monitoring the suspect car because “all the intelligence told us the white cavalier would be carrying the intelligence”.
That decision proved fatal for Mr Caldwell who died two days later.
The white Cavalier was later found burnt out in Co Louth with the tracking device still working.
Hartnett admits that his unit was “wrong footed” by those responsible for killing him.
He hopes the fresh details of the killing will bring comfort to Mr Caldwell’s family.
“Until now, no one had any knowledge of North Det’s involvement in the incident. David Caldwell’s daughter, Gillian McFaul, has been looking for answers ever since that day,” he wrote.
“I hope this provides some.”