On Saturday, September 7, 400 women from across Scotland will gather in the parliament's debating chamber to discuss the gender imbalance in Scottish politics.

Our special correspondent Bernard Ponsonby takes a look at some of the women who have played a key part in Holyrood's first 20 years.

On the day of her death I said this of Margo MacDonald: "Charismatic is an overused word in politics and it doesn't begin to capture the presence and appeal of a politician who connects with the public more than any other MSP."

She genuinely was a one off. "Dusted with magic" was the judgement of her husband Jim Sillars. Margo - she was always known by her first name - was no saint. She infuriated colleagues in the SNP who lost patience with her stubbornness. They believed that she allowed single mindedness to masquerade as principle and all for essentially self-indulgent ends. They had a point,  but only up to a point.

MacDonald's contribution as an independent MSP on issues such as the Holyrood building project, tolerance zones for prostitution and legislation on the right to die mark her out as the most outstanding backbench parliamentarian of Holyrood's first two decades.

She was, of course, a national figure from the 1970s when she was a breath of fresh air in a world dominated by male politicians, many of whom were decidedly tenth rate.

Towards the end of her life she was closest to female Labour politicians. Many of whom she admired, particularly those who were non-tribal.

Susan Deacon was one Labour politician who left parliament in part because of a frustration with the Labour-SNP bun fight which sought to polarise honest policy differences, defining the discourse as a clash of the irreconcilables.

She hated the fact that two left-of-centre parties could not agree on an agenda defining a social floor below which no citizen should fall. After all, was the search for consensus not what the post-1999 politics was supposed to be all about?

Deacon was on the receiving end of briefings mostly organised and executed by men and some of whom no doubt felt threatened that she might eventually torpedo their leadership hopes. She decided to forsake politics for wider public service which is a pity for Scottish Labour, who in recent years would have benefited from her counsel.

Her colleague Wendy Alexander was always a policy wonk rather than a politician. Any journalist or indeed opponent who has watched her in action as she drills down into the detail of policy could not fail to be impressed. As the minister who piloted the repeal of section 28, she can look back with pride that she helped make Scotland a more tolerant place.

Her career, however, serves as a warning to those who come into politics for change based on high principle. Alexander would grow weary of the back-biting and pettiness of internal politics. I hate to depress idealistic younger readers but this is a culture to be found in all parties. Like Deacon, Alexander now undertakes her public service in another field.

Many women politicians have made great contributions over the years. The Liberal Democrat Alison McInnes was an outstanding advocate of her party's justice agenda both in committee and in the chamber. Her reward was effectively to be deselected by her party in favour of a man.

Within the old SNP group, Christine Grahame and Dorothy-Grace Elder were damned by the ultimate promotion-threatening judgement; they were mavericks. Both these women have great attributes to be found in any steely parliamentarian. They see flattery for what it is, they care little for overbearing whips and they are happy to be prisoners of their own conscience.

Grahame's long campaign on Lockerbie is a necessary part of the status quo being challenged. Elder's campaign for those suffering from chronic pain has transcended her time in parliament and is testament to 'the political agitator who is most effective is the one with the greatest staying power'. DGE has it in spades.

Annabel Goldie brought a wit and charm to the Holyrood chamber. One commentator described her as "Chic Murray in a frock". With a twinkle in the eye, and a dedicated line in self-deprecation, she was the antithesis of what the Tories were supposed to be all about.

By dint of opposition caricature they were humourless, hard-nosed, uncaring. And those are just the adjectives I can print. The charge was difficult to pin on the Baroness, who would feign outrage at the attacks with a simple utterance of "what? Moi?".

Of course, the current First Minister is the stand out of all of the women of the last 20 years not least because she has made it all the way to the top. My memory might be playing tricks but I can't recall Nicola Sturgeon pursuing a feminist agenda during her early years in the SNP.

Since taking the top job, however, she has sought to promote an equality agenda for women at home and abroad, helping to reshape the agenda and encouraging young women to believe that all is possible. That's not a bad contribution.

When I first started reporting politics all of Scotland's leaders were men. Until recently three of the four leaders of our main parties were women. The sky did not fall in with change but nor did the temperature of our politics lessen.

The stuffed, mostly overstuffed grey suits of the past are gone. Scotland's Parliament has done reasonably well in the gender-balance stakes. It will have done even better when we no longer talk about it.

Politics is ultimately a battle about ideas. There is no gender-based analysis around that, nor should there be.