The Lothians MSP was a true champion of the Scottish Parliament as an institution in its own right.
She was fiercely protective of its reputation as a forum for sensible debate and considered law-making and never hid her exasperation when she felt it was being used merely as a platform for party politics or point-scoring.
As an Independent, with close friends and allies across the political divide, it was easier for her to stand aloof from the party system.
However, she remained determined to set an example as a parliamentarian.
Indeed, she came to be seen by many as the conscience of the parliament.
She took up the role when she was first elected, becoming a leading critic of the over-budget Holyrood building project.
Throughout her time her love for and respect of Holyrood was demonstrated by her unrivalled understanding of standing orders, the rule book governing parliamentary procedure.
And perceived infringements would invariably provoke an awkward point of order ahead of decision time at 5pm.
Margo also conducted most of her day-to-day business in the parliament, preferring to meet fellow MSPs, constituents and expert witnesses attending committees in her room or in the bar. Working mainly from parliament rather than an expensive rented high street office ensured she was usually at or near the bottom of the annual expenses league table.
The practice also gave the bar its affectionate nickname: Margo's. That and her occasional visits for a glass of cava with colleagues and journalists.
Among the many tributes yesterday, Holyrood's Presiding Officer Tricia Marwick recognised her particular contribution to the parliament over 15 years.
"She was a sparkling jewel in the Scottish Parliament, her contributions were incisive, intelligent and always got to the heart of the issue under discussion," she said.