Teacher and campaigner;

Born: June 23, 1925; Died: October 17, 2012.

Mary Mackenzie, who has died aged 87, was a shareholder whose regular appearances on the circuit of Scottish AGMs inevitably spawned a lexicon of adjectives.

Redoubtable, indomitable, formidable, forthright, demanding – none of them particularly flattering but she didn't give a hoot.

Her habit of turning up and asking awkward questions of miscellaneous boards was part of her one-woman crusade to stand up for fairness and justice, to fight what she perceived as wrong. She recognised that some regarded her as a nuisance but she would not be deterred, raising subjects as diverse as the quality of a floral display in a bank to the lack of women at board level.

She also took the authorities to task over common good assets and went head-to-head with the National Trust over the closure of properties, founding a campaign group to challenge the moves.

Yet, for all her headline-hitting swipes at executives, letters to the media and the Government, she was a fiercely private individual who gave away little of her personal history, once dismissing a query about her Christian name as "no business of the press" and leaving instructions that, on her death, no notice was to be published until after her funeral.

An only child, she was born at home in Edinburgh's Bruntsfield Place, the daughter of a Bruntsfield Union Bank agent and a teacher. She attended George Watson's Ladies College and Edinburgh University where she graduated with an MA.

During the Second World War she worked in a munitions factory and became a temporary member of the Amalgamated Engineering Union. She went on to teach at Edinburgh's Forrester Park High School and Boroughmuir Academy, mainly concentrating on modern studies but also acting as a guidance teacher and providing remedial teaching.

The widespread misconception that she had been a headmistress may have stemmed from what one business reporter described, after she had retired from teaching, as her "tendency to treat bank directors as if they were naughty schoolboys".

After retiring she moved, in 1990, from the capital's Marchmont to Peebles. But she regularly made the car journey to Edinburgh to attend concerts and deal with business matters.

She inherited her passion for music from her parents and played an active role in Scotland's cultural life, particularly in the field of music but also in the arts, theatre and ballet. She endowed a scholarship in memory of Ian Whyte, founder of the BBC Scottish Symphony Orchestra, and was a great supporter of Scottish Opera, enjoying a long and warm association with its founder Sir Alexander Gibson. She also supported Scottish Ballet and several other artistic organisations, and was a member of the National Museum of Scotland and the National Library of Scotland where she was one of the earliest patrons of the John Murray Archive.

A life member of the National Trust for Scotland (NTS), in 2009 she co-founded the campaigning organisation In Trust for Scotland in response to an NTS funding crisis and its plans to close properties. The aim was to force an extraordinary general meeting and attempt to reverse the closure decision. The following year, after a strategic review of the NTS, her motion, proposing greater involvement in governance by volunteers and local members, was passed with the support of the board.

It was typical of her: if she learned of a "wrong" or thought something needed doing, she would simply get on and tackle it.

To this end her shares in numerous companies allowed her access to meetings where she could put her carefully considered questions to those in power.

She became well-known on the circuit of meetings, including those of the Royal Bank of Scotland where, in the row over bonuses, she once observed: "One cannot admire people who require so many inducements and bonuses to do an honest day's work," adding, "one could mention camels and needles."

During one annual Scottish & Newcastle shareholders' meeting in 1992 she took on the then recently knighted chairman Sir Alick Rankin. He had been widely praised for the way in which, over 35 years with the company, he had helped to transform it from regional brewer into one of the UK industry's major players. But she took exception to what she claimed was an increase in Scottish & Newcastle's contribution to the Conservative Party to £70,000. "The chairman's knighthood has been bought at much more than its market value," she commented.

Never one to be fobbed off, she was an avid letter writer and her crusades involved lengthy correspondence to officials in local authorities, MPs and MSPs and media organisations, including The Herald.

She knew she was perceived by some, she said, as "that nosy old bat", but she was a woman who took her responsibility as a shareholder very seriously and she wrote to various company chairmen offering her views on the running of their companies.

Though she called them to account on a range of subjects such as bank closures, pension schemes and staffing policies and had been dubbed "Scotland's most demanding shareholder", she was also respected and apolitical.

What mattered most to her was fairness. And although she was a very private individual she showed great kindness to those who helped her and to those whom she felt needed help.

She lived for her work, her campaigning and for justice and, persistent as ever, was still drafting a letter just days before she died.