The fascinating story of how a single unexploded wartime bomb had a ‘ripple affect’ that led to hundreds of deaths in a school in east London is told on BBC 2 tonight.

East London Advertiser: Spitalfields 1940: Air-raid devastation in Spital Street. Picture: Tower Hamlets ArchiveSpitalfields 1940: Air-raid devastation in Spital Street. Picture: Tower Hamlets Archive (Image: Tower Hamlets Archive)

It depicts the disaster of the South Hallsville School bombing at Canning Town in 1940 which killed a many as 600 men, women and children who were sheltering there.

An investigative wartime journalist looking into the tragedy later met a people’s champion in the East End, Mickey Davis, who was running a public air-raid shelter at Spitalfields Market that historians view as the forerunner to the post-war welfare state.

Tonight’s programme starts with families having to be evacuated when the bomb lands in Martindale Road in Canning Town on the first night of the Blitz on September 7, 1940, but fails to go off.

East London Advertiser: Calder's grandson Gideon interviewed at Spitalfields Christ Church for BBC 2 'Blitz' doccumentary. Picture: Mike BrookeCalder's grandson Gideon interviewed at Spitalfields Christ Church for BBC 2 'Blitz' doccumentary. Picture: Mike Brooke (Image: Mike Brooke)

They are sent “for safety” to the school from where they are to be evacuated to the country as promised. The buses to take them never turn up.

Fleet Street reporter Richard Calder meets the families in cramped conditions and writes in the Daily Herald that “there’s going to be a disaster unless something is done”.

His tragic prophesy comes true the next day when the school gets a direct hit during another German air-raid, killing everyone sheltering there.

East London Advertiser: Calder's grandson Gideon interviewed at Spitalfields Christ Church for BBC 2 'Blitz' doccumentary. Picture: Mike BrookeCalder's grandson Gideon interviewed at Spitalfields Christ Church for BBC 2 'Blitz' doccumentary. Picture: Mike Brooke (Image: Mike Brooke)

“It puts Calder on the warpath as a campaigning social journalist,” explains BBC producer Tim Kirby.

“He calls for ‘a better job’ of looking after people made homeless by the air raids—and this is where Mickey Davis comes into the story.

“Calder goes all over the East End and comes across Mickey’s shelter in Spitalfields Market. He doesn’t just see a community hero doing great things in time of peril, but the outline of what we later come to call the welfare state.”

East London Advertiser: German air-raid devastates Club Row when Stein's clothing factory is wrecked, May 10-11, 1941. Picture: Tower Hamlets ArchiveGerman air-raid devastates Club Row when Stein's clothing factory is wrecked, May 10-11, 1941. Picture: Tower Hamlets Archive (Image: Archant)

Tonight’s episode follows the bomb that fell on Martindale Road that failed to explode.

Stan Harris and Norman Pirie were boys in 1940, but their memories of that fateful night are crystal clear in the programme.

Judy Gregory’s grandmother, uncle, aunt and cousins put their faith in the authorities and wait for evacuation buses that don’t arrive. Hundreds are a sitting-target for the German bombers.

East London Advertiser: Air-raid damage in 1940 in Commercial Road. Picture: Tower Hamlets ArchiveAir-raid damage in 1940 in Commercial Road. Picture: Tower Hamlets Archive (Image: Tower Hamlets Archive)

The link with Spitalfields is Calder’s investigations following the South Hallsville tragedy, when he meets the man known as ‘Mickey the Midget’, just 4ft tall, who ran the market shelter like a social welfare service years ahead of its time.

He includes a whole chapter on Mickey’s shelter in his wartime book Carry On London.

The programme researchers traced Calder’s grandson, university lecturer Gideon Calder, 45, and Mickey Davis’s nephew, East London Advertiser journalist Mike Brooke, who were both interviewed for the documentary in May at Spitalfields Church.

Gideon said after the filming: “My grandfather reported the day-to-day unfolding of wartime life. He looked at what people were doing in their everyday lives and people like Mickey trying to feed people and run the air-raid shelters.

“Something emerged to keep society going. We still live largely in the world created on the back of the Second World War—more caring, where something like the NHS is absolutely vital.”

The East End and the docks bore the nightly brunt of the Blitz for nine months from September, 1940, to May, 1941. But the South Hallsville tragedy triggered a whole chain of events that lead to a government policy change into how to deal with mass homelessness caused by the air-raids.

People believed for years afterwards that the worst civilian air-raid disaster had been at Bethnal Green in 1943 where 173 people died, the youngest a five-month-old baby, in a crowd surging down the narrow staircase for safety during a tragic false alert. Official casualty figure for South Hallsville was 77—but it turned out decades later that closer to 600 people may have died.

Tonight’s BBC 2 Blitz: The Bombs That Changed Britain episode at 9pm is the first of four documentaries, the others looking at “the ripple effect” of a single bomb on Hull, Clydebank and Bristol.