An inquest last week into Sean Harper's death - from multiple injuries sustained in the fall - recorded an open verdict after scathing criticism from the coroner that some people at the University of London Royal Naval Unit party knew more than they were saying.
The secrecy surrounding the Ministry of Defence board of inquiry, in the same building used as a services training base in Kensington, west London, where Sean met his death, is also in keeping with the investigation into his final moments. Detectives even resorted to a spiritual medium to try to get to the truth.
Those close to Sean, a mechanical engineering student, talk of a cover- up.
Most of the events leading up to his death at the party on the night of 13 December are not in doubt. The evening began with Sean and his flatmates, Morgan Thomas and Robert Rule, both 20, setting off from their house in Leytonstone, east London, dressed in black ties and dinner jackets. Tickets came courtesy of Mandy White, 20, a member of the naval unit.
There were 200 guests at the event, drinking and dancing, but by 4.30am, when Thomas and Rule left, numbers had started to thin. By then, all concede, Sean was drunk. The pathologist said he had nearly three times the drink-drive limit for alcohol in his body. He was probably obnoxious, too.
He got into a row with Chief Petty Officer Jonathan Kew, goading the officer: "Go on then, throw me out of the window." Nothing came of it. Within minutes, though, Sean was deliberately bumping into Sub-Lieutenant Simon Bellamy, whose appeals for him to stop were met with a hail of abuse.
Shortly after, Sean was passed going downstairs by a barmaid. No one admits to having seen him alive again.
At 8.30am the police were called because cars had been vandalised in the unit's basement. Damage amounted to pounds 3,500.
Back at Leytonstone, Sean had not returned. By evening the alarm bells started ringing and his flatmates reported him missing. So began an increasingly frantic search for Sean. Fellow-students at Queen Mary and Westfield College, in east London, joined the hunt. Reported sightings proved illusory.
Christmas at Sean's parents home in Newmarket was flat. Decorations and the tree were in place. But Sean's mother, Judy, 50, could not bear to leave the phone. "It was like an umbilical cord," she said.
Finally, on 5 January, a London Underground maintenance crew found the semi-naked body of a man at the bottom of a shaft for the disused Old Brompton station. His shoes lay alongside him. It was Sean.
For Sean's parents it ended the "blackest days", filled with uncertainty about their son's fate. Yet, as Det Insp Alan Wilson and British Transport Police officers began their investigation, new questions emerged.
In interviewing every guest, some under caution, Det Insp Wilson established that glass embedded in Sean's shoes came from the windscreen of one of the damaged cars. His dress shirt, cuff-links in place, had been in the basement car park.
To have fallen down the shaft, which ran from the old station up to the top of the building used by the services unit, Sean must have been on the roof. Unit members maintained the door to the roof was locked. However, a plumber said he probably left a key in the door.
Yet, in 2,000 man-hours of inquiries, Det Insp Wilson failed to nail down Sean's final minutes. "This has been the most frustrating inquiry I've worked on," he said. "We have done so much, but there's a period between 6am and 7am that we can't account for."
His theory, voiced at the inquest, was that a gang from the party chased, or came upon Sean, in the car park. The vehicles were damaged as he ran across bonnets and roofs to escape. His shirt was ripped off in the process.
Sean was then either chased, or taken, up the stairs leading past the bar onto the roof. He may have been locked out, or during a chase seen the ventilation shaft as a means of escape. How his laced-up shoes came off remains unexplained.
"I am certain that someone knows more than they are telling us about Sean's death," Det Insp Wilson said. "The police believe no-one outside the party was involved. With the open verdict the investigation is still live, though our inquiries are finished."
In their Newmarket home the Harpers, barred from tomorrow's inquiry, simply want the truth. "We're not out for vengeance," Mrs Harper said.
White no longer mixes with the unit's officers and is to resign. "I've a feeling that we're never going to get to the bottom of this," she said. "It destroys your faith in people. I wake up thinking of all the possibilities. I hate to think the last part of his life was in fear."