A crewman on HMAS Voyager who narrowly escaped from the wheelhouse of the ship before it sank in 1964 was intimidated into silence for more than half a century by a British naval officer who rose to become an admiral in the Royal Navy.

Alex Hagerty was one of three men in the wheelhouse of the Voyager on the evening of 10 February 1964 when the vessel was struck by its much larger flagship aircraft carrier, HMAS Melbourne. Voyager was cut in half and sunk with the loss of 82 lives.

But Hagerty, now 71, has found the courage to reveal what he believes is crucial evidence of a cover-up of the true cause of Australia’s worst peacetime disaster.

Hagerty believes the collision was caused by a faulty course-and-speed order given by the Voyager’s officer of the watch, Lt David Price, a British naval officer on secondment to the Royal Australian Navy. Price went down with the ship.

After the collision, Hagerty says, he was was taken to Sydney’s naval base HMAS Watson and cowed into silence by its captain, British officer Capt Ian Easton, also on secondment.

Hagerty maintains Easton systematically challenged his recollections and intimidated him into withholding evidence at the first royal commission into the disaster.

Easton, now deceased, later attained the rank of admiral in the British navy and was knighted for his service.

Hagerty was the only survivor of the three men in the wheelhouse of the ship who heard and responded to the final course-and-speed orders given to them in the seconds before the collision.

Hagerty, a member of the HMAS Voyager Survivors Association, is the second survivor to talk to Guardian Australia. Radio operator Allan Hellier was motivated to clear the name of Captain Duncan Stephens, saying he had borne unfair criticism and could not defend himself because he died in the collision. The inquiry into the disaster heard that Stephens was frequently drunk and unfit to be in command of the ship, and on the night of the accident had ordered a triple brandy from his steward.

Hellier revealed for the first time publicly that it was he who drank the triple brandy the captain had ordered for him 90 minutes before the collision because he thought it would help his upset stomach.

When contacted by Guardian Australia, Hegarty also wanted to correct the record about his captain, and agreed he had been unfairly criticised.

“The captain was a lovely skipper,” he said. “He was a good man. He was a fair man.”

The collision

As the Melbourne struck the Voyager amidships, Hagerty was lucky to survive because the wheelhouse of Voyager was on the edge of the direct path of the Melbourne as she cut through the smaller vessel.

The enormous force of the impact rolled the Voyager on to its side, forcing the wheelhouse suddenly under water.

The three men in the wheelhouse were standing no more than a few feet apart but Hagerty does not know what happened to his fellow crewmen. Both died in the disaster.

Hagerty believes the collision was caused by a faulty order given by British naval officer Lt David Price

Hagerty’s memories are clear but recalling them and speaking about what happened still causes him to experience the feelings of the terrifying moment when he thought he would die.

“I heard a bang,” Hagerty said. “The ship turned over. The lights in the wheel house went out. The wheelhouse was instantly full of water.

“The ship was lying on its side and the wheelhouse was under water ... I had cut hands. It was dark, underwater. The ship must have been underwater quite a way for the wheelhouse to be flooded.”

His legs were scratched on the back but he could swim. “I saw light above me while I was still under the water,” he said. “I went towards the light.

“The next minute I was on the surface of the ocean. I don’t know how I got there.”

A lifeboat from the Melbourne picked up Hagerty from the ocean and he was able to climb the boarding nets up the side of the aircraft carrier despite his injuries.

Once he had showered and was given clothes, he was taken aside and asked to write down his recollection of what happened because he had been at an important location on the ship at the time of the collision.

He was given a pen and paper to make notes within two hours of the disaster.

Alex Hagerty’s notes of the Voyager collision, made two hours after disaster struck.

The Daring-class destroyer was constructed with the wheelhouse in the centre of the ship under the bridge to protect the ship’s steering in case of enemy attack.

Sailors in the wheelhouse therefore had no windows and those at the helm had no situational awareness of the vessel on the ocean and had to rely on instructions spoken down a voice tube from the bridge of the ship.

In addition, the ship’s radar was in the operations room on the floor above the wheelhouse, so there was no electronic indication of their position in relation to other ships.

“In the wheelhouse you do what you are told from the bridge – you don’t ask. You can’t see,” Hagerty said. “In front of you is an instrument like a sun clock with an arrow and, as you turn the wheel, the arrow turns as well.

“All I know was we were looking for a wind to come over the Melbourne’s bow so the planes could take off easier with the wind under their wings.”

Hagerty’s notes document the names of the three men in the wheelhouse: himself (ordinary seaman Degenhardt, he has since taken his father’s surname, Hagerty); leading seaman Frank Sharkey and able seaman Stanley Hale.

Hagerty noted the engine doing 160 revolutions per minute and that at 8.45pm Hale had the wheel and that “every minute” Hale was given orders to change the course and speed.

I want the blame put where it belongs. Alex Hagerty, Voyager survivor

Hagerty wrote that at 8.50pm they were given the order to steer 15 degrees to starboard and then, almost immediately, to steer 10 degrees to port.

He then records there were no orders given for two or three minutes.

Unbeknown to him the ships were closing in on each other. Hagerty then records that 10 seconds before the collision he heard the officer of the watch, British naval officer Price, “screaming out”.

Hagerty then heard the captain call out “What the fuck’s he done now?” but he only wrote down the captain’s order: “Full ahead both. Both engines.” This recollection was verified by two other survivors who heard the captain’s words through the voice pipe connected to the wheelhouse.

Survivors of the disaster were taken to Sydney on HMAS Melbourne and were given one week’s leave.

Hagerty, 17, went home to Newcastle where he had grown up in the busy port city and had dreamed of a life at sea.

Once he returned to duty the following week, Hagerty was assigned to the navy’s new hydrographic survey ship, HMAS Moresby, in preparation for her commissioning in March 1964.

He was having nightmares about the disaster but was not given medical help. Instead, a sick-berth attendant told him to “go ashore and drink some beer” so he could sleep at night.

Soon after Hagerty was separated from his fellow crewmen and posted to HMAS Watson, the royal Australian navy training base at South Head on Sydney harbour.

Here the captain of HMAS Watson, British officer Easton, spoke to the 17-year-old each day, challenging his recollection of the events leading to the collision and putting to him a different scenario of events.

Hagerty has told Guardian Australia that he was angry that his evidence was challenged.

“I was bloody pissed off. I was suffering and [Easton] wanted me to tell bloody lies to suit him,” he said. “Every day he would quiz me and suggest I was a bit confused. This went on the whole time until I finally got to the royal commission.”

Hagerty said when he appeared at the royal commission his version of events was brought into question by the government barrister who had knowledge of his conversations with Easton. The 17-year-old capitulated under duress. He was not called to give evidence at the second royal commission.

Hagerty was discharged medically unfit from the navy at the age of 20 and given an invalid pension.

Lifelong trauma

More than 50 years on, Hagerty wants his Voyager captain exonerated.

“I want the blame put where it belongs,” he said.

Hagerty believes Price’s inexperience partially led to the disaster.

Price had joined the Royal navy in 1952 working on minesweepers and small vessels and had experience of manoeuvres in which vessels turn together but he had not worked on a destroyer. He joined Voyager’s crew on 2 January 1964, less than five weeks before the collision.

“He had never done night exercises on a destroyer in his life,” he said. “He is supposed to be looking and seeing what is needed to be done. If the Melbourne says ‘we are turning’, it’s his job to pass it on to us [in the wheelhouse].”

Hagerty believes Easton deliberately intimidated him to deflect blame for the disaster from a fellow British officer.

Although he survived the disaster, Hagerty says the trauma he experienced has affected him throughout his life.

“I’m alive but I didn’t survive,” he said. “The lucky ones are the ones who died that night because they’ve not had 54 years of survivor guilt.”