A HUNDRED years ago this month, with the Great War at its height, a Clyde-built converted troopship, the SS Mendi, was sunk, with a catastrophic loss of life, more than 600 men perishing.

But the 12-year-old cargo liner was not the victim of a German torpedo or mine. The vessel, its holds crammed with over 800 enlisted black troops from South Africa bound for the Western Front, was sunk in the fog-bound English Channel by a much larger British mailship that was being sailed recklessly fast by its captain and advanced on it at full speed.

The collision caused such damage that the Mendi sank in less than 20 minutes. As a new book marking the centenary of the disaster puts it: "The loss of the Mendi occupies a special place in South African military history. This is not because it remains one of the country’s worst disasters at sea. Nor is it because hundreds of lives were lost or because it was a troopship ... Rather, it is because the men it was carrying were not fighting troops and they were not white; they were members of the South African Native Labour Corps (SANLC)."

The support troops were part of a huge force of recruits from China and the British Empire tasked with supporting the fighting troops by building roads, bridges, trenches and railways.

The Mendi, a 370 foot long steamship that could accommodate cargo and passengers, had been built for the Edinburgh-based British & African Steam Navigation Company at the Linthouse, yard of shipbuilder Alexander Stephens in Glasgow. It was launched in June 1905 and went on to play a key role in Britain's trade with Africa, making 53 round trips between Liverpool and West Africa between 1906 and 1916.

After its final voyage to Lagos, Nigeria, in October 1916 it was converted into a troopship as part of the British government's war effort.

In January 1917 it left Cape Town with the enlisted SANLC labourers for the long voyage to Le Havre in France. The officers, all of whom were white, included an NCO Colour Sergeant Robert Alexander MacTavish, a South African-born officer whose father had come from Aberdeen.

On February 20 the Mendi set sail from Plymouth across the fog-bound Channel. Shortly before 5am the next day, south of the Isle of Wight, it was struck by the Darro and immediately began taking on water. Some of the men escaped on life rafts or lifeboats but several hundred others found themselves clinging to the rafts or floating in their lifejackets.

Led by the Mendi's escort, HMS Brisk, attempts were made to rescue the men, and though 267 were saved, everyone else was lost, either in the collision or from hypothermia in the unusually cold February waters.

The shocking loss of the Mendi was, however, largely forgotten about in the war's aftermath. But South Africa has never forgotten those black troops who perished. In 1995 President Mandela invited the Queen to unveil a memorial in Soweto, one of a number across South Africa. And the country's national award for bravery is now known as the ‘Order of Mendi’.

More than 50 years after the disaster the Mendi wreck was discovered in 1974 and in the last few years its importance has started to become recognised in the UK. It is now a protected war grave.

Graham Scott, of Wessex Archaeology, who wrote the book with South African archaeologist John Gribble, spoke about South Africa's abiding interest in the tragedy. "It's all to do with the country's history and the way it impacts on its people now. These men on the Mendi were treated unequally in life – and in death, too. South African members of the SANLC didn't receive the British War Medals that the British Government gave to all those who served in the war.

"These members hoped their participation, their sacrifices, would result in favourable treatment in South Africa after the war, and they were bitterly disappointed when it didn't,", he said.

"The Mendi came to be associated with various initiatives designed to promote the interests of the black community and it developed into a focal point for protest and resistance, to the extent that it worried the [white] South African government.

"It came to symbolise the struggle for equality and social justice, but in the dark days of the 1980s, with risings in Soweto, the idea of black men fighting a white man's war didn't resonate too well with a lot of the younger activists.

"The Mendi's legacy thus became quite controversial, but since the end of apartheid it has been celebrated and commemorated by the government. It's an inspiring example of sacrifice and an aspect of the Great War that, until the centenary commemorations, we didn't hear a lot of, about the role of non-white people from the Empire and dominions."

Scott added: "As archaeologists we use the story of the Mendi and the men on board as education resources and talk about contemporary issues such as equality and social justice."

The Mendi will be remembered in this country between February 17 and 21, including, on the 21st, a Royal Navy warship and a South African warship visiting the site of the tragedy and, weather permitting, Royal Navy divers laying a flag on the wreck.

* We Die Like Brothers: The sinking of the SS Mendi, by John Gribble and Graham Scott (Historic England, hardback, £17.99) is published on Feb 17.