Among the many relatives of the dead present was 94-year-old Ellen Leckie, who travelled from Levin with her nieces for the service.
Mrs Leckie's husband Jim Leckie, of Dunedin, was one of the 764 men who perished when Neptune struck four mines in an uncharted minefield off the coast of North Africa and sank.
Mr Leckie was aged 24 and the couple had been married for only a year.
Following songs from the Dunedin Returned Services Choir and speeches from Lt-cmdr Bruce Walker, the commanding officer of HMNZS Toroa, George Fergusson, the British High Commissioner, and the Chief of Navy, Rear Admiral David Ledson, the memorial on Customhouse Quay was unveiled by special guest Norma Hudson, of England, the daughter of the sole survivor of the disaster, British sailor John Norman Walton.