It was described as one of the worst tragedies Leeds ever experienced – an explosion at the Barnbow Munition Factory in Cross Gates, which killed 35 women – and yet it had to be kept quiet at the time.
The date was Tuesday December 5, 1916 and, as per usual, several hundred women had begun their shift at the sprawling factory, which itself was so large it had its own railway station complete with 820ft platform.
Hundreds of women from Leeds, Selby, Harrogate, Wakefield, Tadcaster and Wetherby were employed at the factory.
When it opened in 1914, more than 130,000 people applied to work there but only 16,000 were taken on, at a rate of 1 8s per week. However, when a bonus scheme was introduced, output trebled and many women were taking home between 10 and 12 – big money back then.
But the work was hard and often dangerous.
Jobs included filling shells, cartridges and other components for the war effort. Chemicals used in the work meant many workers' skin turned yellow, leading to them being called 'canaries'.
Workers often had to strip to their underwear and don buttonless smocks and caps. All had to wear rubber gloves during the eight-hour shifts.
The factory, however, never closed and was worked round the clock. It even had its own farm, with 120 cows producing 300 gallons of milk a day.
On December 5, at 10.15pm, as the night shift had just got underway, some shells containing high explosives were taken to Room 42. The noses of the shells were placed on by hand and screwed down. Then they were put in a machine to be further tightened.
Moments later there was a violent explosion, killing 35 and injuring many more.
Most were dreadfully mutilated in the blast and identification was only possible by the identity discs worn by workers.
Despite the danger, men and women rushed into Room 42 to drag survivors free – a mechanic, William Perkin, of Nesfield Walk, Leeds, was commended for rescuing around a dozen girls.
Many of the injured were later taken for a period of convalescence at Weetwood Grange. Although rumour of the explosion criss-crossed the surrounding towns and villages, not a word of it appeared in the papers.
There was one clue: in the Yorkshire Evening Post, death notices read "killed by accident".
It was a full six years later that even the slightest details about the tragedy were officially made public.
Arthur Peck, formerly of Brownberrie Avenue, Horsforth, was a young engineer at the time.
He later recalled: "I came on duty early the next morning. Work was going on as normal but Room 42 was a bloodstained shambles.
The accident is believed to have happened when a shell exploded as it was being fused, probably because it had been too tightly screwed down."
He added: "In a thunderstorm, all work had to stop. Absenteeism was rare and in one big flu epidemic the workers were dropping at their benches and being carted off to hospital.
"There were two further explosions, in March 1917, killing two women and May 1918, killing three men but apart from that our only real fear came during a Zeppelin raid. We were told it dropped its bomb somewhere near Harewood."
One of the managers at the factory was Herbert Chapman, who went on to manage Arsenal. Winston Churchill was said to have visited Barnbow, which became Britain's premier shell factory and between 1914 and 1918 and churned out 566,000 tons of finished ammunition.