At 4.14pm on a fine day in early November 1927, the 40m Greycliffe departed Circular Quay on its scheduled Sydney Harbour run to Watsons Bay.

Known as "the school boat", the steam ferry had a number of students among its estimated 140 passengers but there city workers and other commuters aboard.

A small contingent of naval personnel and shipyard workers joined the ferry at its first stop at Garden Island.

The 7600-ton Union Steamship Company vessel Tahiti departed its berth at Darling Harbour a short time later bound for Wellington and San Francisco with 300 passengers and crew.

Just short of Bradleys Head, well inside the harbour, the Tahiti struck the Greycliffe on the port side, cutting the 16-year-old timber ferry in half, casting her passengers and crew into the water and sending the shattered boat very quickly to the bottom.

Forty of the ferry's passengers were killed and many of the survivors were hospitalised. It took three weeks to recover all the bodies.

The majority of the victims were from Vaucluse and Watsons Bay, and the disaster struck deep in these communities.

Dubbo-born but now Switzerland-based genealogist Steve Brew has researched court and maritime records to reconstruct the events that led up to this terrible accident, and has done so in a most meticulous and readable manner.

His interest in the Greycliffe-Tahiti disaster stems not just from a love of nautical history but also from his relationship to the pilot of the Tahiti, Capt. Thomas Carson.

Three judicial hearings and an appeal over the ensuing four years all provided different findings on the collision but it was Capt. Carson, who lived at Watsons Bay where so many of the victims had come from, who received much of the public blame.

All the hearings were told that the Tahiti appeared to be exceeding the harbour speed limit at the time of the accident and that the Greycliffe has altered course to port shortly before the impact.

Both points were strenuously denied by the respective crews.

While the laws of the sea stipulate that an overtaking vessel has a responsibility to keep clear, it also requires all ships to keep a proper lookout, particularly before making a course change.

On appeal, blame was attributed 33 percent to Tahiti and 66 percent to Greycliffe.