By Justin Parkinson
BBC News political reporter
Ms Swinson says she has sometimes felt pigeonholed
The Liberal Democrats were going at it hammer and tongs.
It was 2001 and the party was furiously debating whether to adopt all-women shortlists for parliamentary candidates.
The venerable ex-cabinet minister Baroness Williams was arguing in favour, using the traditional, rhetorical approach to win over waverers.
On the other side, a recent university graduate called Jo Swinson adopted a more direct tactic.
She wore a T-shirt proclaiming: "I am not a token woman."
'Don't call me Baby'
Fast forward seven years and Ms Swinson is the member of Parliament for East Dunbartonshire.
If she had a T-shirt on now, rather than a suit, the slogan might be: "I am not a token young person."
Ms Swinson, at 28, is the first MP to have been born in the 1980s.
The term "Baby of the House" is sometimes used to describe the UK's youngest legislator.
But Ms Swinson said: "I don't like that at all. I would just call myself the youngest MP."
Liberal leader David Steel was 26 when he became an MP
With some honourable members in their eighties and plenty in their sixties and seventies, the Commons is not the most youthful working environment.
Ms Swinson, sitting in the cramped Westminster office she shares with her researcher, said: "Sometimes I think I'm pigeonholed. It still amazes me what excuses people use to bring up my age.
"Once I was asking about the minimum wage for young people and a government minister joked that I was interested because I was one of them.
"Another time I was talking about the desperate unpopularity of the poll tax in Scotland. A Tory said that, surely, I was too young to remember.
"But it was such an awful time that, even though I was only about 10 years old at the time, I could recall it vividly."
Ms Swinson studied at the London School of Economics and worked in the marketing department of the Hull radio station Viking FM before entering full-time politics.
She follows in a tradition of young Liberal, SDP or Lib Dem MPs. Former Lib Dem leader Charles Kennedy was elected at 23, while Liberal predecessor David Steel entered Parliament a week before his 27th birthday.
Ms Swinson said: "In Parliament and politics it seems that people think you are young forever. At 40 you are considered young.
"But look at what other 28-year-olds are doing. My sister became a consultant at the age of 33. When I worked in the media, the programme director was 25. At 28, a lot of people have done a lot in their professions."
Ms Swinson first ran for Parliament in 2001, aged 21, contesting the seemingly unwinnable Hull East seat of the then deputy prime minister, John Prescott.
She said: "During the whole campaign I never met him. I suppose he was busy at the time.
"I was, too, as I had to work part-time in the mornings and campaign for the rest of the day. I never expected to win it, though.
"Despite losing, it was that campaign that made me decide I really wanted to be an MP.
"Politics had always been a hobby rather than a profession for me. I only ran the first time after someone suggested I had a go. But as the campaign went on it took hold of me and I realised what I really cared about was politics."
Emily Benn is a parliamentary candidate at the age of 19
In the 2005 election Ms Swinson contested the seat of Dunbartonshire East, where she had grown up. She took it from Labour with a 4,061 majority.
Ms Swinson said: "While I was campaigning I had to move back in with my parents for eight months, working part-time. I couldn't have afforded to run for Parliament and pay the rent.
"I think it's hard for anyone. It's often forgotten that candidates don't get paid.
"If you spoke to losing candidates after elections, you would find many of them in a large amount of debt."
In 2006 the minimum age for becoming an MP was cut from 21 to 18, raising the prospect of teenagers in Parliament.
Tony Benn's 19-year-old granddaughter Emily Benn has been selected as the Labour candidate for East Worthing and Shoreham.
Ms Swinson said: "Good on her. I hope we get a lot more young candidates. I also think people should be able to vote at 16.
"In fact I also would reduce the age at which someone can run for Parliament to 16. I don't see why we should call for one and not the other."
She added: "I think we need a diversity. We need more people from all backgrounds.
"There are a huge number of Oxbridge-educated lawyers elected as MPs when they are middle-aged. There is not a single MP who has paid tuition fees.
"We have a large part of the population with debts from these or who face working well into old age because of pension changes, but there is no person in Parliament who shares, or will share, their experience.
"In general there's a real bubble around Westminster. For instance, when we talk about the credit crunch, it is about the large-scale economics and the theory.
"It's when you hold a constituency surgery and sit across the table from someone who's having real problems that it brings it to life."
Ms Swinson recently became a Lib Dem foreign affairs spokeswoman and is a member of the Commons environmental audit committee.
Surely it must be a little tiresome having so much to do when other people of the same age are out enjoying themselves?
"The hours of the job have an impact on your life. If I want to go to a friend's wedding, I have to make sure months in advance that I don't have a surgery scheduled. But I'm lucky that I'm doing something I love.
"There are bits of the job that are dry and the pace of progress can be frustrating. People can take years to get the government to change their minds.
"I think one of the problems with politics now is that people are getting used to having an impact on things instantly.
"If you vote on X-Factor, the results come out soon afterwards. If you vote in a general election, things take a lot longer to change."
One benefit of being the youngest MP is that there is a good chance of a career long enough to make a difference.
Will Ms Swinson try to match some of the Titans of the Commons such as Winston Churchill, who served for 65 years, save for a few career breaks provided by the electorate.
Or will she go for the record of Charles Villiers, Wolverhampton's MP for 63 years continuously from 1835?
She said: "The short answer is that I don't know. I suppose I want to stay an MP as long as I think I can contribute something and my constituents still want to elect me."
At least Ms Swinson has the comfort of knowing that - if she wins again at the next election - it should be someone else's job to wear the T-shirt of anti-tokenism.