Just three days into her job as a reporter, Clare Hollingworth could not have expected she'd land the biggest scoop of her career.

After elbowing her way into an industry in which she had few connections and little experience, she landed a job as a journalist for the Daily Telegraph. But determined to prove her capabilities and worth, Hollingworth persuaded her editor to send her to Poland to report on the build-up to war in August 1939.

In the city of Gleiwitz, on the Polish border, she spotted something unusual: hundreds of German tanks lined up, passing through a valley. She stood in front of what appeared to be Germany invading Poland, with the tanks waiting for the whistle blow that would order advance. Hollingworth ran to a nearby building and picked up the phone to call her friend Robin Hankey, who worked at the British Embassy.

"Robin," she said. "The war's begun!"

Hankey dismissed her claim. It couldn't be true, he insisted, as the governments were still in negotiations. To prove she was telling the truth, Hollingworth stuck the phone out of the window so he could hear the tanks moving past. Convinced, he swiftly alerted authorities, who then had the unusual task of telling the Polish government that their country was about to be invaded.

Hollingworth had just alerted the world that World War II had started.