More than 100 people including relatives of the British sailors and representatives from the British, Australian and German naval forces, gathered for a remembrance service today to mark the 67th anniversary of the frigate's sinking.

The eight British sailors were on secondment to the Royal Australian Navy and on board Sydney when it was sunk by the German raider HSK Kormoran off the West Australian coast on November 19, 1941, killing 645 crew.

Like the families of the Australian sailors, relatives of the British men never knew where the watery grave of their loved ones was until March this year when the ship's wreckage was found 207km north-west of Geraldton, off WA's midwest coast.

Just one sailor's body was found, buried on Christmas Island.

The unidentified sailor's remains were reinterred yesterday during a moving ceremony at Sydney's official memorial overlooking the Indian Ocean at Geraldton in WA.

Retired medical researcher Ruan McWilliam's English uncle, Lieutenant Commander Michael Singer, was 32 years old when he died and one of 15 crew members whom experts believed could have been the mystery sailor.

Mr McWilliam, who attended the remembrance service at London's St Clement Danes church, provided DNA samples earlier this year when efforts were underway to identify the sailor.

However, the result was a negative match and the sailor's identity remains unknown.

Mr McWilliam, 76, said despite the result he was "amazed and thrilled" by the recent discovery of Sydney's wreckage 2500 metres below the ocean's surface.

"All of a sudden the whole thing has come together," he said.

"The whole story has been quite extraordinary.

"This time a year ago it was just past history. We thought the whole thing had been laid to rest."

As well as having British soldiers serving on board, HMAS Sydney was built in England in 1935 before setting sail for Australia a year later.