"The Russians were hunting us down. They had a list of names, including ours, and they were closing in." Mstyslav Chernov and his colleague Evgeniy Maloletka were trapped in a hospital surrounded by tanks. As gunmen stalked the corridors, the staff gave them scrubsThe clothes worn by medical staff. to help disguise them. Then, as dawn broke, a dozen soldiers burst in. "Where are the journalists?" they demanded.

"I looked at their armbands, blue for Ukraine, and tried to calculate the odds that they were Russians in disguise," Chernov reported yesterday. "I stepped forward to identify myself. 'We're here to get you out,' they said."

He and Maloletka were the only journalists left in Mariupol to report on the attackers' crimes. That was why the Russians were desperate to find them.

"If they catch you, they will get you on camera and they will make you say that everything you filmed is a lie," a policeman told them. "All your efforts and everything you have done in Mariupol will be in vain."

Chernov has reported from many war zones, including Syria and Iraq. On the eve of the Russian invasion, he and Maloletka, a photographer, headed for Mariupol, knowing it would be an important Russian targetThe city is strategically important because of its position on the Sea of Azov, which connects to the Black Sea..

Only a quarter of the city's 430,000 inhabitants managed to get outMost people stayed, according to Chernov, because they did not believe that the war would actually happen.. "One bomb at a time, the Russians cut electricity, water, food supplies and finally, crucially, the cell phone, radio and television towers," said Chernov.

Cutting communications achieves two things. First, people panic because they do not know what is going on, causing chaos.

"ImpunitySafety from punishment. It derives from a Latin word for penalty. is the second goal. With no information coming out of a city, no pictures of demolished buildings and dying children, the Russian forces could do whatever they wanted... I have never, ever felt that breaking the silence was so important."

Chernov and Maloletka risked their lives to record everything. For days the only place they could get a satellite phone signal was beside a shell hole. Before long, said Chernov, "I had seen so much death that I was filming almost without taking it in."

On 9 March the pair witnessed twin airstrikes. "We watched smoke rise from a maternity hospital. When we arrived, emergency workers were still pulling bloodied pregnant women from the ruins."

As they wondered how to get their images of the atrocity to the outside world, a policeman appeared. "This will change the course of the war," he said, and led them to a place where they could connect to the internet.

Furious at being exposed, the Russians claimed that the report had been fakedBoth the Russian embassy in London and the Russian ambassador to the UN tried to discredit the report.. So on 11 March, Chernov and Maloletka set out for the hospital where the surviving women were being treated. It was there that they found themselves surrounded. The walls were shaking with artillery fire as the Ukrainian soldiers led them to safetyThe journalists escaped the city in a convoy of civilian cars, but had to pass through 15 Russian checkpoints. . 

In his anthologyA collection, usually of writing. It derives from a Greek word for a collection of flowers. Eyewitness to History, John Carey notes: "All knowledge of the past which is not just supposition derives ultimately from the people who can say 'I was there.'"

Yes: Public opinion is hugely important in guiding events, and eyewitness reports help shape it. Vivid accounts of the Blitz played an important role in persuading the US to enter World War Two.

No: Eyewitness reports stir up emotion, but the crucial decisions are made by hard-headed politicians who work out what can actually be achieved. Chernov and Maloletka's reports will not save Mariupol.

Or... Eyewitness reports may not make a difference at the time, but are incredibly valuable afterwards, both for historians and for prosecutors who are trying to bring war criminals to justice.