Knowing the suicidal task they now faced, they looked at one another and said: "We're for it tonight."

Because rather than run from the bombs, the four men had to put themselves directly in the line of hellfire.

Hitler's revenge

A vengeful Adolf Hitler had deliberately selected Canterbury to be the victim of this "terror attack".

The Führer had been stung by the success of recent RAF assaults on German cities, led by Air Marshal Sir Arthur "Bomber" Harris.

Hitler wanted the Luftwaffe to retaliate, vowing to “repay blow with blow”. He ordered that targets be selected with the "greatest possible effect on civilian life", particularly "cultural centres".

His generals used the Baedeker Guide for German tourists to pick out cities which most embodied British cultural history.

Bath, York and Norwich were blitzed, with hundreds of people killed and thousands of homes destroyed. In a raid on Exeter, its medieval cathedral was seriously damaged.

So as the four Canterbury fire-watchers - Tom Hoare, Alfred Burden, Joe Wanstall and Tom Shaw - heard the alert on June 1, 1942, they knew what was coming.

Showing astonishing bravery, at about midnight 80 years ago today, they made their way high up onto the roof of Canterbury Cathedral.

Their mission was to prevent the iconic landmark from being destroyed in the flames.

Looking across the streets below, they would have seen the full horror of the Baedeker Blitz.

A city in flames

For two-and-a-half hours, waves of bombers came over Whitstable, and the people of Canterbury experienced complete terror.

At first, the south of the city was alight. RAF fighters and anti-aircraft guns were in action, but the Luftwaffe got through, dropping thousands of bombs.

Buildings everywhere were engulfed in flames and came crashing down.

As the fire-watchers were busy picking up incendiaries from the Cathedral roof and throwing them to the ground below, other nearby landmarks were obliterated.

The Rose Hotel in the high street and the Royal Fountain Hotel in St Margaret’s Street were among those destroyed.

The M&S in St George's Street somehow survived. But the birthplace of Christopher Marlowe, further along the road, was not so lucky. The "Kitty Marlowe" statue, erected in honour of the playwright, was also blown off its pedestal.

Two churches were gutted – St George’s and St Mary Bredin – and St Martin’s and St Thomas’s RC churches were damaged.

'Debris was falling around the house'

The fire-watchers would also have seen the flames rising from hundreds of homes.

Among the terrified residents was 12-year-old Sheila Curtis, nee Attwood, in Querns Road.

As the warning was called, she rushed downstairs with her mother and sister and went under their Morrison table shelter.

"We felt the house shake as a high-explosive bomb landed in the garden five or six houses away," she told KentOnline's sister paper, the Kentish Gazette.

Her neighbours Mr Kemp and Mr Woolgar, who had been outside, were killed.

“Soon after my father came and told us our house was alight and we needed to get out," she said.

An oil bomb had dropped on the shed and splattered the roof where incendiaries were already burning.

Her father took her sister out through the back door - but before Sheila and her mother could follow, the burning ceiling fell down and blocked their way.

They ran back through the house to the front door, only to find it was jammed.

"The roof timbers were well and truly alight by this time, and debris was falling around the house," she said. "We were terrified."

Thankfully, her father was able to make it to the front of the house and kick the door down so they could escape.

They took shelter next door but could still hear their furniture and belongings dropping through the burning floors of their home.

The family eventually made it into an Anderson shelter three doors down.

"It took in the neighbours from at least five houses, so there were about 21 people in there, including children," Sheila added. "The men mainly stood outside – quite a risk."

One of Sheila's neighbours on that fateful night was Eddie Peake, then aged 14.

“I was in bed when I heard what sounded like horses racing over cobbles – but it was actually slates falling off an already burning roof," he said.

“I found I couldn’t move because the ceiling had fallen in on my bed.

“I looked out of the window and it was light. I know now it was because of the flames.”

One of the biggest bombs ever dropped in Kent

As the city burned around the fire-watchers, one plane swooped low over the precincts, and incendiaries fell onto the roof of the Cathedral.

The men sprang into action and pushed the bombs off the roof to burn on the grass.

The smoke across the city was so thick, that many didn't know at first whether the Cathedral had survived.

Daylight revealed a four-ton bomb, one of the heaviest ever dropped in Kent, had fallen near the entrance to the Warrior’s Chapel, and the stained-glass windows in the nave were blown out.

As the dust settled, a vast crater measuring more than 20ft deep was there for all to see.

Fifteen other bombs had landed nearby and the grass all around was burned black.

But due to the men's heroism - and divine intervention with a south-east wind pushing the bombs slightly off course - the Cathedral was still standing amid the flames.

Once the Luftwaffe finally left, a fifth of the city had been bombed.

Forty-three people lost their lives and almost 100 were wounded.

The city's streetscape also drastically changed, with 800 buildings destroyed and1,000 seriously damaged.

More than 200 firemen from across the county tackled the blazes and worked non-stop for 24 hours alongside rescue workers.

Other heroes on the night included air raid wardens, soldiers, ambulance drivers, police, the Women’s Voluntary Service, members of the Boy Scouts and other youth organisations who carried messages across the city.

Members of the Civil Defence and troops aided by locals helped dig out people trapped in the rubble.

Eddie Peake recalled: “We made our way down Longport to the old hospital, which was being used as a clothing centre, and I was given a pair of socks!

“The houses opposite the old hospital were all burning, so was the former Payne Smith senior school, which was on the corner of Longport and Lower Chantry Lane.

“There were so many displaced people, all walking about homeless and dazed.”

An iconic photograph of the devastation was captured by Anthony Swaine, who climbed the Bell Harry Tower of Canterbury Cathedral to take the picture with a box camera.

“I knew it was forbidden by the government to take pictures but I just could not believe what I was seeing," he later told the Gazette.

“You can’t imagine how it was, you can’t. Half a city burning, no air – you couldn’t breathe for the thick smoke. You would hear people calling out and shouting help, help. I never want to go through that again."

There were two smaller follow-up raids on the nights of June 2-3 and June 6-7. After they were over, within 11 acres of the city 49 people were killed and 46 seriously injured. A total of 697 people were made homeless.

Honouring the Cathedral heroes

The survival of Canterbury Cathedral during the Baedeker raid was largely down to the courageous fire-watchers.

Their leader, Tom Hoare, who died in 1957, was awarded the British Empire Medal in 1944 for his services in the Blitz. He was presented to the King and Queen during the royal visit in 1946.

It is from his diary that we are able to get a true sense of the terror the men must have felt.

He wrote: “It was about midnight when the alert sounded and we said to one another that we were for it tonight.

“We could hear the roar of the planes overhead and when we looked up we saw flares shoot up into the sky from them, and high explosives and incendiaries began to fall.

"They seemed to be coming down like hailstones.”

Their heroism has become legendary, and a campaign started by the Kentish Gazette, called Remember Our Blitz Fire Watchers, resulted in the unveiling of a carved stone memorial plaque to them in the cathedral in 2004.

Among the other fire-watchers whose names were given to the Gazette were Ernest Southon, Bill Gardiner, George Easton, John Musty, Walter Page, Henry Child, Sidney Sladden and James Boulden.