A century on: the mysterious cause and tragic legacy of London’s biggest explosion

View of A, B, C and D silos, Royal Victoria Dock following the explosion. © Museum of London / PLA Collection

It was the most destructive explosion ever to blast London. A century ago, Silvertown, a small community in east London, was devastated by an explosion at a TNT factory so big that is was heard in north Norfolk and Cambridgeshire. Entire streets were destroyed, 73 people were killed and hundreds were injured. As World War I raged across the Channel, it was a terrible echo of the horrors taking place on the continent.

The following vivid account was published soon after the disaster (in a leaflet raising money for a church that was almost entirely destroyed by the explosion):

A few minutes before seven, on the evening of January 19, 1917, people who happened to be out of doors in London noticed a vivid red glow in the sky in an easterly direction … [in Silvertown] many of the people were standing at the doors watching the fire that had broken out, and not realising the terrible danger they were in.

And it really was terrible danger. The fire that had appeared as a vivid glow was just the preamble to a much more destructive tragedy, as the blaze ignited a huge stockpile of TNT, destined for munitions on the Western Front.

Suddenly there was a deafening roar, a fountain of flaming debris was projected high into the air and this spread out like a fiery rose, dropping death and destruction over the whole district. The force of the explosion sent pieces of machinery, some weighing several tons, flying through the air with the result that cottages and factory buildings that were not wrecked by the concussion, were crushed and battered by the hail of fragments that came raining down upon them.

Several streets of houses were converted into heaps of rubble in a second. Those that escaped total destruction remained as mere skeletons among the wreckage.

Worse still, the blast ignited a chain reaction, causing fires that swept through a neighbourhood that soon emerged dazed from the rubble to be confronted by the tragedy’s terrible human cost.

General view of sheds, Royal Victoria Dock after the blast. © Museum of London / PLA Collection

The scene immediately after the explosion beggared description. The burning debris had started fires in many of the factories and mills nearby, which became roaring furnaces as the night progressed. In all directions, people who had escaped serious injury were picking themselves up in a dazed condition. Mothers were frantically looking about for their little ones, many of whom were buried in the ruins, while on the pavements were the bodies of the pedestrians who had been struck as they were walking along.

As a spectacle, England will probably never see its equal. In all directions, great buildings were blazing, fire engines and ambulances were dashing up from all parts of London, hundreds of volunteers were at work rescuing the injured and searching the ruins for bodies. Homeless people were wandering off to neighbouring districts where every available hall had been thrown open to give them shelter.

England’s horror

The (anonymous) author likened the scene to ruined villages along the firing line of the Western Front, as well they might, as the cause was exactly the same high explosive used in the shells that destroyed dozens of French villages. Some very moving accounts of bravery and suffering have been gathered recently. Photographs of the torn girders among the rubble of ruined factories and houses in Silvertown might remind later generations of Ground Zero following the 9/11 attacks in New York, or perhaps a current scene of destruction in Aleppo, Syria.

So why was TNT being purified for shell-making in a highly populated area, surrounded by factories processing combustible paint, oil, wood and sugar, when the danger of explosives factories was so well known?

Compared to gunpowder, trinitrotoluene (TNT) is relatively stable and only becomes explosive when put under great pressure or heat. In 1910, it was even exempted from the 1875 Explosives Act, which would have applied a host of planning and safety regulations on its manufacture.

The government was also doing whatever it could to provide high explosives for the huge guns on the Western Front. A shortage of ammunition led to the “shell scandal” of 1915 which brought down the government and a successful campaign by David Lloyd George for a national munitions policy. The result was a coalition government with Lloyd George as minister of munitions, and a huge demand for existing factories to be quickly converted to munitions production.

An explosive issue

The Brunner Mond Factory in Silvertown had been built in 1893 to produce caustic soda. Production had stopped in 1912 which meant a fully equipped chemical plant lay idle. When approached by Lord Moulton who headed the Explosives Supply Department, Brunner Mond & Co agreed to convert it to TNT purification, despite the fact that 3,000 people lived nearby.

An improvised surgery in the vestry of Barking Road Wesleyan Methodist Church. © Newham Archives and Local Studies Library

A subsequent account published by Brunner Mond in 1923 claimed this permission was reluctantly given:

The company strongly expressed their reluctance to carry out such a dangerous manufacture in a densely populated district; but the urgency was so great they eventually consented.

Lord Moulton was well aware of the danger to civilians, but later explained that the Brunner Mond works were effectively requisitioned because “we could see no other way of obtaining purifying works within the time that they were necessary”.

General view of damage from silo granary Royal Victoria Dock. © Museum of London / PLA Collection

If the war effort was mainly to blame for the location of the TNT plant, what actually caused the terrible explosion? To help answer this we now have access to the detailed government report, kept secret until 1957, into the likely cause of the disaster which took evidence from 36 experts and witnesses immediately after the disaster.

By this time, the danger of TNT explosion in the purifying process was well known – the inquiry report lists 29 previous fires or cases of accidental TNT detonation. In 1915, a big TNT explosion occurred at the crystallising plant at Ardeer, Scotland causing one death and several injuries. A committee looked into the causes and recommended that TNT should no longer be exempt from the 1875 Explosives Act, but this was ignored by the government. Had they taken this advice, perhaps the Silvertown explosion may never have happened.

On the night of the Silvertown explosion there was a fire on the upper levels of the building, where the TNT was melted in a pot as part of the purification process. Four or five minutes later, the TNT in the melting pot exploded, along with more TNT stored on the site – 53 tons in total. The two workers near the melting pot died in the explosion which meant that it was impossible for the inquiry to discover exactly how the fire started.

Alien enemies?

At the time, many Londoners thought it was the result of a Zeppelin raid, but there were no sightings anywhere in the country that night (there had not been an air raid for months). Another common explanation was arson by a German spy, and the inquiry looked into this carefully. They found adequate security and no “alien enemies” working there. A 57-year-old German man worked at Brunner Mond, but not in the TNT plant. He also had been living in England since he was ten, had an English wife and 12 children, three of whom were serving in the British Army. Moreover, he had left at 6pm that day and was considered beyond suspicion. However, the inquiry did identify a major security issue that may have been exploited by an enemy.

Tragedy: a memorial to the fallen. Gordon Joly via Flickr, CC BY-SA

Raw TNT came to Silvertown from a factory in Huddersfield and took several weeks to arrive via rail, barge and lorry. The inquiry found that barrels and kegs of TNT often arrived broken, and the contents were not checked before melting. The inquiry reported that it would have been quite easy for an enemy agent to add a chemical, like a freely available stick of caustic soda coated in varnish, into a barrel along the route. As caustic soda can ignite molten TNT as temperatures as low as 82C, it could easily cause a fire in the melting pot. No evidence or accounts of sabotage have emerged in the German records, but it remains a possibility.

A more prosaic, and I think more likely cause, identified by the inquiry was a detonation spark caused by friction or impact. A government safety inspection, just three weeks before the explosion, revealed some unsafe practices. TNT was left on the floor around a hopper and if degraded, it could have been ignited by a boot nail, grit or something metal. There were no regulations to prevent grit on the floor and, astonishingly, metal tools (which could easily create sparks) were found in the TNT building.

Another possibility was a fire caused by alkali left over from the caustic soda making years before, but we will probably never know exactly what caused the fire that night. There is no doubt, however, that the resulting explosion had huge consequences.

A terrible legacy

The hardest hit were the families and friends of the 73 victims, who ranged in age from four-months-old to 76 years. Hundreds more had to cope with injuries. Six hundred families were made homeless and an estimated 70,000 properties were damaged in some way. The government paid compensation to the victims and repaired remaining houses in Silvertown (the patched up Victorian terraces can still be seen today).

The fire station opposite was blown away along with two incredibly brave firemen who ran to put out the fire, knowing full well it was an explosives factory (a memorial can still be found at the new fire station). There is also a memorial to the workers who died in the explosion on the site of the factory.

The inquiry recommended that security of TNT should be improved and it should be stored in magazines away from processing plants. It also called for the inspection system to be strengthened and that TNT should be regulated as an explosive under the 1875 Explosives Act.

Personal tribute: a small offering. Toby Butler, Author provided

But it took another explosion at a TNT factory, which killed more than 40 people at Hooley Hill in Manchester, for action finally to be taken on the report findings. The Special Service Branch of the War Office was put in charge of munitions factories to improve security and in August the Ministry of Munitions finally classed TNT as an explosive under the Explosives Act. All future factories would require a licence following rigorous safety checks and procedures.

We may roll our eyes at “health and safety” these days but anniversaries like this remind us that some of the industrial and workplace regulations we inherit are based on lessons learned the hard way, and paid for with people’s lives.


The Museum of London will be releasing a digitised photo album of the 24 images of the explosion damage taken by John H Avery for the Port of London Authority. Newham Archives and Local Studies Library holds archives on the disaster and has organised a touring exhibition in Newham.