Ken Earl sat through nearly 50 days of evidence at the inquest into the death of fellow Porton Down "guinea pig" Ronald Maddison.
Ken Earl heads the largest group of Porton Down volunteer veterans
But he couldn't quite make its denouement - a little matter of cancer intervened.
He had surgery as the marathon hearing neared its end, and he spent the final days, including the coroner's summing up and jury's verdict, recovering at his Kent home.
Prostate cancer was the latest in a series of health blows that have seriously blighted his adult life.
The former television actor found his career hampered by a worsening spinal condition and other illnesses.
He can't help but believe his health problems are linked to the nerve agent dropped on to his arm in the same gas chamber as Mr Maddison was to sit two days later.
"I have got skin problems - I have had a carcinoma removed from my left arm, bang opposite where the stuff was put on my skin.
"Since my 30s, I have had a condition called spondylosis, which limits my movement.
"I have had multiple hepatic cysts on my liver...
"And depression, which I believe most people who have been subjected to nerve agents suffer from: there have been a lot of suicides [among fellow Porton Down veterans].
"Then they gave me an ECG just before my recent operation and found I had atrial fibrillation (a heart irregularity)." He has now developed an embolism on the lung, which has constrained him still further.
"I come from very tough stock, but I have been ill most of my life," he explains. Having been a fit young man, playing rugby at his RAF station, he now walks with a stick - when he's not laid low by the legacy of one or other of his illnesses.
Yet Mr Earl, now 71, sounds absolutely genuine when he says he feels lucky. "At least I'm alive and I have had three-score years and 10. Poor old Ronald Maddison got only 45 minutes."
He was just 19 when he volunteered to go to Porton Down, answering, he insists, a call to servicemen to volunteer to help with research into the common cold.
"Why would a young student actor want to do anything that might damage my health? I would be a fool. I was a medic, so the common cold interested me. It was something worthwhile."
But the Ministry of Defence has always denied misleading any of the servicemen and points out a police investigation failed to establish any evidence to support suggestions they were lured under false pretences.
Mr Earl, an RAF medic on national service, was also attracted by the prospect of a weekend pass and an extra 15 shillings, enabling him to travel from the RAF Service Hospital in Wroughton, near Swindon, Wiltshire, to his girlfriend in Maidstone, Kent.
He arrived at Porton, an establishment near Salisbury, not far from his home base, on 2 May, 1953, the same week as Mr Maddison, a leading aircraftman in the "regular" RAF.
And he recalls the moment he became an unwitting test bed for the lethal sarin nerve agent which claimed his comrade's life.
"We were put in a chamber. Something was dripped on to our arms. It was unbelievably claustrophobic wearing a respirator. I had never worn one, other than during the war.
"I couldn't wait for it to finish. But I couldn't feel anything (being dripped on to his arm). No after-effects - just unbelievably sweaty and hot.
"I didn't want to say, 'stop' because I didn't want to appear a coward. We were fit young men who could take anything, we thought."
The MoD, which subsequently arranged for former volunteers' health to be monitored by a team of experts, says the use of volunteers for such tests was a different proposition in those post-war and Cold War climates.
Mr Earl went on to become a successful actor, appearing in a variety of programmes, including Dr Who, No Hiding Place and virtually all the cult action-adventure shows of the 1960s and '70s, including The Saint, The Avengers and The Professionals.
But his life changed dramatically in 1999 when he read a newspaper report that police were investigating a young man's death at Porton Down in 1953.
Soon he was leading a group of fellow volunteers who had been at Porton between 1939 and 1989 and who believed they, too, had undergone tests on nerve and biological agents.
Chemicals were tested on human guinea pigs at Porton Down
The Porton Down Veterans' Support Group now has around 500 members, including relatives of some who have died since joining. Many other vets do not belong to his group but also attended the base.
And while no-one knows what Mr Maddison was told, Mr Earl and many more Porton Down vets are adamant they were answering a call to take part in common-cold experiments... and certainly nothing more risky or sinister.
He is dismayed by the Ministry of Defence's entrenched attitude, even during the inquest, which heard from some 100 witnesses and dealt with thousands of pages of documents.
"What I didn't anticipate was so much resistance from the MoD. I can't see why they don't admit we were duped. There are too many of us for it to be anything else."
Now, while some of his members talk of compensation, Mr Earl is focused on a lesser goal - an apology and public inquiry to confirm once and for all what so many British servicemen were subjected to.
"Although it is disgusting what they did at the time, it is down to informed consent. We knew nothing - and why should they have told us anything? From their point of view, we didn't need to know anything.
"But they misled me - and there are too many of us. Thousands of us."