A man has been arrested in relation to a series of attacks that targeted judges of the Family Court of Australia, claiming four lives and injuring dozens of others more than three decades ago.

The NSW homicide squad arrested Leonard John Warwick, 68 at Campbelltown at 11:30am on Wednesday. He is assisting police with their inquires.

It is a breakthrough in one of the most notorious crimes in NSW history and follows the decision by the homicide squad to recommence their investigation into the Sydney bombings and shootings that claimed four lives and injured dozens of others between 1980 and 1985.

Mr Warwick was publicly named by a state coroner as the prime suspect at two inquiries but was never charged.

The NSW homicide squad recommenced its investigations in 2012 into the series of attacks leading to Wednesday's arrest of the former fire fighter, who was engaged in a Family Law custody dispute in 1979.

Police have been examining the murder of Mr Warwick's brother-in-law, Stephen Blanchard, who was shot in the back in February 1980. Four months later, Family Court judge David Opas was shot at point-blank range when he answered the doorbell to his home in the eastern Sydney suburb of Woollahra.

Justice Opas had previously made adverse findings against Mr Warwick during a custody battle.

His replacement at the Family Law Court, Richard Gee, was then targeted in March 1984 when a bomb, the equivalent of 50 sticks of gelignite, exploded on the front door step of his Belrose home in Sydney's north.

The explosion, which levelled the house but from which Justice Gee and his two children managed to escape relatively uninjured, occurred on the same day Mr Warwick's matter was to be heard in court.

The next month the Family Law Court building in Parramatta was targeted by a bomb attack. No one was injured.

While Justice Gee recovered from his injuries, his matters were looked after by Justice Ray Watson. His Greenwich home was targeted in July 1984.

His wife, Pearl Watson, was killed instantly after she untied a plastic bag attached to the front door of their home, triggering a bomb explosion.

Then prime minister Bob Hawke and premier Neville Wran announced a task force of 50 detectives. It spent two years examining suspects.

In February 1985 an attempt was made on the life of Mr Warwicks' ex-wife's solicitor.

It prompted Mr Warwick's ex-wife, Andrea, to leave Sydney with her children with the assistance of her sister. Her sister, who was Jehovah's Witness, arranged through her congregation to move the family to Forster on the NSW Mid North Coast.

Almost six months later, a massive explosion rocked the Jehovah's Witness Kingdom Hall in Casula, in Sydney's south-west. There was a congregation of 150 inside. Father-of-three Graham Wykes was killed instantly. Another man, David Winder, sustained life-threatening injuries.