SECRET symbols on Stirling’s pies and the story of how a medicinal posset revived Bonnie Prince Charlie feature in a series of films made to celebrate the 900th anniversary of the Royal Burgh.

They include how Kippen was once home to the world’s largest grapevine and how the Stirling Jug or Scots Pint was the national standard for liquid measure, holding the equivalent of three imperial pints.

Now one of the oldest artefacts of the Royal Burgh, the Stirling Jug was manufactured at Edinburgh Castle in 1511 by Robert Borthwick, whose main job was casting cannons for the defence of the realm. It became the national standard for liquid measure as the burgh was at the centre of a thriving brewing industry.

Planted a few centuries later in 1891, the Kippen Vine covered 5000 square feet and needed four glasshouses to cover it. It produced more than 2000 bunches of grapes a year, with many sold to Harrods in London.

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“There were always competitions at the time to grow pineapples and grapes – exotic things that you wouldn’t expect to find in Scotland,” historian and archaeologist Dr Murray Cook told the Sunday National.

Later, when grapes were no longer considered such a luxury, the vine became a tourist attraction with an estimated 20,000 visitors annually and peak daily numbers in excess of 1000. Maintenance of the vine was extremely labour-intensive and it was cut down in 1964 but cuttings survive in greenhouses around the country.

As for the pies, they were a feature of Stirling’s Guildry Trade Association, the oldest continuous body in Scotland after church and crown.

“The story goes that every time members attended the trade guild, they were given a pie with a backwards ‘4’ on it so they could prove to their wives they were at the meeting rather than getting drunk,” said Dr Cook, who contributed to the films which have been made on behalf of Forth Valley Food and Drink, with funding from Scotland Food and Drink’s regional fund.

Dr Cook said that the reason the symbol was a backwards 4 is unknown but was probably related to Stirling’s trade with the Balkans. When Stirling was made a Royal Burgh by King David in 1124, its location on the River Forth helped to make it prosper.

“It was one of the most successful burghs in the 12th century because it occupied such a strategic location,” said Dr Cook. “The economy exploded but then boats got bigger and other ports took its place.”

Perhaps one of the most interesting tales in the films is the posset given to Bonnie Prince Charlie when he arrived in poor health at Bannockburn House in January 1746.

The story is that it was given to him by Clementina Walkinshaw, the niece of the owner of the house, Sir Hugh Paterson.

Researcher Cat Bradley said that at the time, possets were made from warm milk mixed with spices, sugar and alcohol.

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“The oral tradition says Clementina nursed him back to health and, fully restored, he carries on with the rising – and I can imagine if you are unwell and have been travelling in mud and rain for weeks at a time and you are then in a nice warm house with a pretty lady serving you a hot drink, that might not be such a bad deal,” she said.

However, there appears to have been a lot of tension between the prince and his generals at that point.

“Some of the primary sources indicate he wasn’t paying as much attention to military matters as should have been, with the insinuation that he was distracted,” she said.

Clementina’s sister was a lady-in-waiting to the queen so it was also thought she might be spying on the Jacobites and keeping the queen informed of their plans.

Yet when Charlie fled to the continent after Culloden, he wrote to Clementina asking her to join him, which she did against the wishes of her family.

“She was an unmarried lady so hanging out with someone known to be free with his love was seen as quite scandalous,” said Bradley.

Clementina remained the prince’s mistress for eight years and was the mother of his only legitimised child, Charlotte, who took care of Charlie in his last years.

More tales about Stirling’s food and drink heritage can be seen in the films.