The last member of a family line that has led Irn-Bru maker AG Barr for more than a century is to step down from the helm of the soft drinks firm today.

Robin Barr's 31-year tenure as chairman will end at the firm's annual meeting in Glasgow and the position will pass outside the family for the first time in the company's history.

Mr Barr, 71, is one of only two people who know the secret recipe for "Scotland's other national drink".

Although he is stepping down as chairman, Mr Barr will continue as a non-executive director and come in to mix Irn-Bru. He will eventually pass on the formula to his daughter Julie, the company secretary.

mfl Alongside the iconic Irn-Bru, the firm's brands also include Tizer, Rubicon, Strathmore and Orangina.

Although Mr Barr is one of only two people to know the Irn-Bru secret, the formula is said to have been written down and stored in a bank vault somewhere in Scotland.

The chairman - who joined AG Barr in 1960 when his father Robert Barr was at the helm - will be succeeded by chartered accountant Ronnie Hanna, who has served on the company's board for five years.

He steps down after reporting an "excellent start" to the current year, with like-for-like revenues "well ahead" of the previous year.

The outgoing chairman said: "I am delighted to leave the business in such good shape and in the hands of a capable and experienced team."

Mr Barr has presided over a period of diversification for the company, most recently adding the fruit juice range Rubicon to the Cumbernauld-based firm's portfolio.

His departure marks the end of a line of family chairmanships, stretching back to the company's inception in 1875 when his great-grandfather Robert Barr embarked on a new direction for the family cork-cutting business with the production and sale of "aerated waters", as soft drinks were called at the time.

Andrew G Barr first began selling "Iron Brew" in 1901 and shrewd marketing quickly saw the company rise to be Scotland's top soft drinks seller.

When Robert Barr took over the firm in 1947, he renamed the drink Irn-Bru after concerns over new food labelling regulations - the drink did contain iron, but was not brewed.

The current business has won praise from City analysts for its steady performance. Investec's Nicola Mallard said: "AG Barr has proved to be a consistent deliverer, outperforming the soft drink category, even in a tough climate."

:: Robin Barr is one of only two people in the world that knows Irn-Bru's recipe, which is held under lock and key in a vault in Switzerland. It is the only piece of paper in the world that contains the 32 ingredients which make Irn-Bru. The mysterious second person who knows the recipe, is not allowed to fly on the same plane as Mr Barr.

:: AG Barr launched Iron Brew in 1901 with Adam Brown, a highland athlete, on the front of the label.

:: Iron Brew decide to change the label of its product in 1922, replacing Adam Brown with a Cambridge rower.

:: AG Barr's advertising campaign The 'Adventures of Ba-Bru and Sandy' featured in Scottish newspapers from 1930. The campaign became the longest running advertising cartoon in history, lasting until the 1970's.

:: Iron Brew was removed from sale from 1942-1947 because of the Second World War. Drink manufacturers were only allowed to produce six standard drink recipes, such as lemonade, because of a shortage in raw materials. Iron Brew was not a designated standard drink and went off sale.

:: Iron Brew was re-launched in 1947. AG Barr's decided to change the product's name to Irn-Bru because of proposed new food labelling regulations. The regulations said the brand name had to be literally true, and while the soft drink contained iron, it was not brewed. The company, therefore, re-launched with the name Irn-Bru.

:: Irn-Bru revealed a tartan inspired label available only in England in 1969.

:: Irn-Bru cans were first released onto the market in 1974.

:: Due to Irn-Bru's supposed cure for hangovers, Billy Connolly released an ode dedicated to Mr and Mrs Barr "for saving my life on so many Sunday mornings" in his 1975 album Cop Yer Whack For This.

:: The Irn-Bru 'Made in Scotland from Girders' posters were released in the mid 1980s.

:: Irn-Bru's own tartan received accreditation from the Council of the Scottish Tartans Society in 1997.

:: Irn-Bru was first manufactured in Russia in 1998.

:: In 2007 Irn-Bru announced a three year sponsorship deal worth £3m with the Scottish Football League.

:: In February 2009 Irn-Bru becomes the official sponsor for the Rugby League and Sky Sports' Super League coverage for 2009.