This month – on 19 January – sees the centenary of the biggest explosion London has ever experienced. It was reported at the time that the shockwaves could be felt in Essex and heard as far away as Southampton, Kent and Norwich, while witnesses spoke of a “huge fountain of flame” reaching into the night sky. While London had experienced aerial bombardment from zeppelins since 1915, what happened in Silvertown dwarfed the scale of the bombs that had been dropped on the city.

Silvertown is a riverside area of East London that was densely populated in 1917. Sitting directly south of the Royal Victoria Dock, it lay outside of the area governed by the Metropolitan Building Act of 1844, which prevented ‘harmful trades’ from setting up business within the city, a move intended to protect public health. Without the restrictions of the Act, and conveniently located near both the docks and a ready supply of labour, Silvertown had become popular for companies making and handling noxious substances such as caustic soda, petroleum and creosote.

One such company, Brunner, Mond and Co chemical works, made caustic soda until the outbreak of the First World War; it soon found itself under government pressure to convert to something more conducive to supporting the war effort. In September 1915, the company management gave in to this pressure and agreed to adapt the premises. The factory was soon helping to fulfil the heavy demands for munitions along the Western Front by making several tons of TNT, an explosive used in artillery shells, every day.

There were reservations about producing volatile materials in such a crowded urban area, however. FA Freeth, chief scientist for Brunner Mond, later wrote that while the manufacturing process used in the factory worked well, it was “manifestly very dangerous”. He went on to record that, “At the end of every month we used to write to Silvertown to say that their plant would go up sooner or later, but were told that it was worth the risk.”

Shortly before 7pm on Friday 19 January 1917, these reservations were proved to have all-too-solid foundations. A fire broke out in the melt-pot room at the top of the factory, where crude TNT was emptied in large quantities through a hopper for processing. The exact cause of this fire has never been pinpointed, although rumours of arson by German spies or a zeppelin bombing raid circulated afterwards. Within minutes the fire had reached the main store of TNT, igniting 50 tons of high explosive, which ripped through the factory and surrounding buildings.

Munitions worker Hetty Sands later described how she had a fortunate escape from the explosion. At about 6.40pm that Friday evening, she went to check if workers in the melt-pot room required any more supplies, before heading out on her usual tea break with her friend Ada Randall. Soon after leaving the building, she heard something that she later described as like “an iron door being banged”. Ada saw that the top of the factory “was all afire”, and the two women started to run, before being knocked unconscious by the force of the blast.

A large part of the factory and those inside it were almost instantly destroyed. The explosion extended outward through the densely packed streets that surrounded the Brunner Mond works, destroying or badly damaging other factories, docks and warehouses and over 900 local houses. Across the Thames on the Greenwich Peninsula (now the site of the O2 Arena), a gas holder exploded, sending a fireball into the night sky. Molten metal from the heat showered down for miles around. Somewhere between 60,000 and 70,000 buildings were damaged as a result of the Silvertown explosion, costing around £250,000 – an enormous sum at the time.

What was worse was the human impact. The explosion caused the death of 73 people, including those working at the factory, dock workers, fireman based at the local station, and local residents, including children. Several hundred more were injured, 94 of them seriously, and many local families were left homeless. Had the explosion happened earlier the day when more workers were on shift, the death toll could have been an awful lot higher.

One rescuer who attended the scene of the disaster was Salvation Army Captain William Manson, then in charge of the Silvertown Corps, who worked at the site from the Friday night to the following Sunday, reportedly without a break. An interview with him that appeared in the Birmingham Daily Post on 23 January, recorded Captain Manson’s recollection: “I saw a man lying in the road with his head blown off. Hearing screams from a house, I groped my way along the passage and found a woman and two children half buried. The woman was pinned down by a beam. Two men arrived in a few minutes, and after three-quarters of an hour’s hard work digging and sawing we managed to extricate the woman. One of her feet had been severed. The nose of one of the children was cut right off; the other child was scarcely hurt at all. In the adjoining house I found two children dead.”

The day after the Brunner Mond works was destroyed, an Explosion Emergency Committee was established to coordinate relief and rebuilding works. Within weeks, 1700 men were employed in repairing and rebuilding houses for those who had been left homeless by the explosion. The government ended up paying out around £3 million in compensation to those affected by the disaster. While this was not the only munitions disaster of the war – or even the costliest – it certainly left a lasting impression on the East End.