It sounds like the back-cover of a spy thriller but these were the circumstances surrounding WWII's deadliest civilian disaster.
For decades, little was known about the Bethnal Green Underground tragedy but a new memorial close to the site of the disaster hopes to provide a fitting place of remembrance for the victims and a way to shed light on the secrets that surrounded their deaths.
On 3 March 1943, shortly after 8pm, 173 people were crushed to death as they rushed into the bomb shelter deep in Bethnal Green's Underground Station.
According to witnesses, the tragedy occurred during a test firing of a new British weapon, rather than a German attack.
Babette 'Babs' Clark was 11 years old at the time. She was heading into the shelter with her sister and mum.
"It was pitch dark because of the black-out, raining like mad," she told Sky News, "and suddenly there was this terrible noise like thousands of rockets going up and, as they went up, they whistled like bombs did.
"And what was happening was they were testing a rocket gun in Victoria Park, but nobody knew."
"Unbeknownst to us at the top [of the stairs] a lady had slipped at the bottom of the stairs and pulled a man with her. And of course there were 19 steps going down and it was like a domino effect. They all fell on top of one another."
According to the Stairway to Heaven Memorial group, as people rushed into the station to escape what they thought was a bombing raid, around 300 people ended up wedged into the stairs leading to the platforms, leaving many crushed or suffocated.
Babs' sister was able to pull herself and Babs to safety but in total, 27 men, 84 women and 62 children died in the tragedy.
Dr Joan Martin was a Casualty Officer at a nearby hospital and saw dozens of injured, and dead, being brought into the ward.
Dr Martin, now 103 years old, told Sky News: "It was quite the most awful thing that happened, and the awful thing was that it didn't need to happen.
"We were sworn to secrecy about it. The most important thing was that we didn't tell anyone."
The wartime government used the Official Secrets Act to conceal the scale of the tragedy.
It said the news, if publicised, would dent public morale at a critical juncture in the war.
The government also suppressed details about the lack of basic safety measures, such as lighting and handrails - details that the local council had previously reported to them.
The suggestion was that this was an accident, sparked by public panic.
It's taken decades of campaigning by a local charity to uncover the truth and get approval, and funding, for an official memorial.
Until now, a small plaque at the entrance to the tube station has been the only reminder of what happened here.
Architect Harry Paticas has designed a teak and stone structure engraved with the names of the victims. It is just a few metres from the Tube station entrance and a poignant, and long overdue, place to remember those that lost their lives here.