Keep calm and carry on to the Australian War Memorial

Designed by the Ministry of Information in 1939, the Keep Calm and Carry On poster was part of a series of propaganda posters to strengthen morale on the home front during the Second World War.

Almost 2.5 million copies were printed, but the poster was held in reserve, to be issued only if Germany invaded Britain.

As a result, most people never saw the poster during the war, and the majority of copies were pulped after it ended in 1945.

Nearly 60 years later, Stuart Manley, the co-owner of Barter Books in Alnwick, Northumberland, was sorting through a box of dusty old books that he'd bought at auction when he found a folded up piece of paper at the bottom.

"I opened it out, and I thought, 'Wow, that's quite something,'" he said in an interview with The Guardian newspaper in Britain. "I showed it to [my wife] Mary, and she agreed. So we framed it and put it up on the bookshop wall. And that's where it all started."

It was the year 2000, and the couple hung their copy of the poster behind the cash register in their second-hand bookstore in an old railway station in the far north of England.

"It had a really nice feeling about it," Manley told The Independent. "As soon as we put it up, people started commenting. A number of customers wanted to buy it, but we refused to sell."

Instead, Manley confirmed that the design was out of copyright and decided to make 50 copies. But the printer said it wasn't worth it: "We had about 50 copies in mind, but 500 was the printer's minimum. We thought we'd just hold onto the rest for as long as it took to flog them, but within a year they'd sold out."

Manley told The Telegraph in Britain: "I thought, we'll sell them eventually." But after the poster appeared in The Guardian's 10 Favourite Things list in December 2005, Manley sold 9000 in a month.

"All hell broke loose," Manley told the BBC. "Our website broke down under the strain, the phone never stopped ringing and virtually every member of staff had to be diverted to packing posters."

Then in 2009, as the global economic crisis took hold, the poster started to appear on everything from t-shirts to mugs and became the inspiration for countless parodies and memes. The BBC even asked if it was "the greatest motivational poster ever", describing the simple five-word message as "the very model of British restraint and stiff upper lip".

"We thought it was a bit of fun and that after a while it would die down," Manley told The Independent. "But it didn't."

In 2011, the poster even became the subject of a trademark dispute after a European ruling allowed an English businessman to trademark the phrase.

Other original copies of the poster survived in the collection of the Imperial War Museum, and the British archives, and 15 were discovered in 2012 when a descendant of a member of the Royal Observer Corps brought them along for an episode of the television show Antiques Roadshow.

Another of the original copies of the poster – as well as those that were issued alongside it ('Freedom in in Peril' and 'Your Courage, your Cheerfulness, Your Resolution will Bring Us Victory') – was donated to the Australian War Memorial by the British government.

That poster is now on display at the Memorial as part of the Hearts and minds: wartime propaganda exhibition.

According to senior curator Alex Torrens, it is one of the most iconic wartime propaganda posters in the national collection.

"It's unusual in that it was designed as part of a series of posters that were seen as being insipid and patronising when they came out at the beginning of the war, but now we associate it with that very 'Britishness' of the slogan, of advocating a stiff upper lip in times of terror, and with that British resoluteness of Londoners during the Blitz," Torrens said.

Today, the poster is instantly recognisable and it is one of more than 10,000 wartime propaganda posters held by the Memorial.

"Perhaps the simplicity of its design – the white writing with the simplified crown at the top against a fire engine red – is also something that is attractive to people in the 2000s, when it was actually republished," Torrens said.

"It would be interesting to think how many of our visitors, especially the younger generation, know that Keep Calm and Carry On was a wartime poster."

Hearts and minds: wartime propaganda is on display in Anzac Hall until April 5.

Curator Alex Torrens will present a free gallery talk at the Memorial at 11.30am on April 5, 2018.

Claire Hunter is a feature's writer with the Australian War Memorial.