Wuhan in Central China was placed under a strict lockdown on January 23 this year.
All of its 11million citizens were ordered to stay in their homes as the deadly coronavirus ravaged the city.
Covid-19 is believed to have originated in the city's Huanan Seafood Market, which sold both seafood and wild animals, had more than 1,000 stalls and was the largest market of its kind in Central China.
The first people to fall ill with the novel coronavirus were admitted to hospital almost a month before the strict measures preventing travel were introduced.
BBC's Panorama: China's Coronavirus Cover-Up examines exactly how Covid-19 leaked from China and spread around the globe, claiming 600,000 lives, infecting 16million people and leaving the world's economy decimated.
Initially those who had become ill, traders from the seafood and wild animal market, were displaying unusual pneumonia-like symptoms.
Then, on December 27, lab results showed they were all suffering from a coronavirus very similar to SARS.
The World Health Organisation had toughened its rules on reporting a potential new coronavirus outbreak following the devastating SARS outbreak in 2002, which killed 800 people.
It ordered that any possible new strains or outbreaks should be reported to the WHO within 24 hours.
China didn't confirm it was dealing with a coronavirus outbreak until the start of January - and even then waited a further six days before confirming it was a new strain of the deadly infection.
More worryingly, it also seems China hid the fact the disease could be spread via human to human - with medics and scientists told to stay silent about the situation.
Even so, doctors tried to alert each other to the seriousness of the new coronavirus - and were ordered to stop.
Prof Li Lanjuan Zhejang was one of the early advisors to the Chinese government following the initial outbreal of coronavirus.
She told the BBC: "To announce contagiousness before it was confirmed would have caused public panic. Only after we had ascertained the facts could we release the information to the public."
Liu Xiaoming, the Chinese ambassador to the UK, has also defended his government's actions in the early days of the pandemic.
He said: "When you have something that’s dangerous to people’s help there is always the risk of panic - we needed to make sure there was no panic."
By January 12, cases of coronavirus had been diagnosed in Shenzhen, thousands of miles away from Wuhan.
Professor Kwok-Yung Yuen, from the University of Hong Kong and the man responsible for identifiying SARS back in 2002, was sent it to help.
He said: "I know how efficient the virus was spreading. If you don’t make use of every hour, then you are in big trouble."
When he arrived in Wuhan, Prof Yuen visited the market where the first cases of Covid-19 are believed to have infected humans - and what he found worried him.
He explained: "They told me the place was very dirty, a lot of animal decal material, rats running around."
But the market had been closed three weeks previously and thoroughly disinected. While samples had been taken from some of the animals sold there, they hadn't been from many others.
Prof Yuen said: "When we went to the market there was nothing to see because it was cleaned, the crime scene is already disturbed so we can’t ID any host that is giving the virus to human."
Also says officials stonewalled on the numbers of people infected and if medical staff had been infected.
Prof Yuen added: “I do suspect they had been doing some cover up locally at Wuhan. The local officials were supposed to be relaying info didn’t do that as rapidly as they should. If they had done that faster, this disaster would be 100 times less."
Health bosses warned as early as January 14 there was a risk of possible human to human transmission of coronavirus - but those in power played down the risk.
By mid-January, the people were gearing up for their biggest national public holiday - Chinese New Year.
In Wuhan alone, 5million people left the city to go and visit family and friends - and the government did nothing to stop them.
Matthew Henderson, from the Asia Studies Henry Jackson Society, told Panorama: "They need to tell the people of Wuhan, but they don’t. They allowed people to travel from the scene of what they know is an epidemic."
Profesor Andrew Tatem, from the University of Southampton, who studied mobile phone data coming out of Wuhan, added: "This is the equivalent of our Christmas and it’s the largest movement of humans on the planet."
And those leaving Wuhan weren't just travelling around China, they were making journeys around the world.
On January 18, China claimed it had had just 45 confirmed cases of coronavirus, although British experts put that figure at closer to 4,000.
In Wuhan alone, 5million people left the city to go and visit family and friends - and the government did nothing to stop them.
Matthew Henderson, from the Asia Studies Henry Jackson Society, told Panorama: "They need to tell the people of Wuhan, but they don’t. They allowed people to travel from the scene of what they know is an epidemic."
Profesor Andrew Tatem, from the University of Southampton, who studied mobile phone data coming out of Wuhan, added: "This is the equivalent of our Christmas and it’s the largest movement of humans on the planet."
And those leaving Wuhan weren't just travelling around China, they were making journeys around the world.
On January 18, China claimed it had had just 45 confirmed cases of coronavirus, although British experts put that figure at closer to 4,000.
Prof Li recommended the lockdown and still believes Chinese government acted at the right time.
She said: "It was felt when the epidemic in Wuhan threatened the entire country, so the timing was just right."
However, Prof Tatem believes that if China had acted earlier, the world could have seen a very different outcome.
He explained: "If the same interventions that were put in place on 23 January had been put in place on 2 January, we may have seen a 95% reduction in the number of cases."
China says fewer than 5,000 citizens died due to the firm measures it took - but these statistics have not been independently verified.
Globally, coronvirus has killed 600,000, infected 16million people and crippled the world's economy.
- Panorama: China's Coronavirus Cover-up is on BBC Two at 7:30pm tonight.
