Falsely-accused Guildford Four member Paddy Armstrong has requested an active role in the resumed pub bombs inquest.
In a submission, he told Surrey Coroner Richard Travers his involvement could help the families of those who died get to the truth of what happened.
His application was opposed by two police forces, the Ministry of Defence and the family of victim Ann Hamilton.
Five people were killed and a further 65 were injured when the IRA blew up two pubs in 1974.
The Guildford Four served 15 years in jail in what became one of Britain's biggest miscarriages of justice.
In his submission to a pre-inquest review, Mr Armstrong claimed important evidence gathered by police after the bombings had been "nothing but a work of fiction" and "guesswork", and said he could comment on the credibility of the evidence.
He said he wanted the truth for himself and the families of those who died.
Henrietta Hill QC, representing Mr Armstrong, said issues to be explored by the inquest - including the times, locations and who was with the victims - were all part of the criminal trial against her client.
She said Mr Armstrong could offer "significant assistance" to the inquiry.
However Oliver Sanders QC, counsel to the inquest, said the prosecution case against the Guildford Four rested entirely on their confessions and did not explore events that night.
Beatrice Collier, for Surrey Police, said Mr Armstrong seemed to envisage himself as a "quasi-expert witness", but told Mr Travers: "If he were to take that role it would risk usurping your own."
James Berry, for the Met, said Mr Armstrong had no knowledge of any of the matters within the inquest scope and no connection to anyone who died, while Edward Pleeth, for the Ministry of Defence, said: "He had no real-time involvement with the bombings whatsoever."
Christopher Stanley, from KRW Law, solicitor for the Hamilton family, said: "The deceased should be at the heart of the inquest process."
Appearing without counsel, he said the family had not been at the heart of any investigation into the Guildford pub bombings for 46 years.
Ms Hamilton died alongside Caroline Slater, 18, William Forsyth, 18, and John Hunter, 17, in the first blast at the Horse and Groom on 5 October, along with 21-year-old plasterer Paul Craig.
Mr Stanley also told the inquest the Hamiltons had approached the Legal Aid Agency, Home Office, Ministry of Defence, Cabinet Office for Veteran Affairs, and Royal British Legion for legal funding, without success, while social media and crowdfunding appeals could not be relied on.
He said: "It's important to have it on the record that it's a very sad and sorry state of affairs."
Mr Travers said he would rule on Mr Armstrong's application by the end of November.