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.

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 two are not allowed fly on the same plane together.

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.

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.