This past week I delivered a cheque to HM Treasury for £50billion.
That's the amount we could add to London's economy if women were able to work the hours they want to, at the same rate of pay as men.
It's a sizeable sum. Indeed, our cheque was so big that passers-by laughed as I and the brilliant women running for WE in the GLA elections carried it up the steps of the government's exchequer.
Sure, it was a fun thing to do. But I'm deadly serious about the opportunity Londoners are missing. And I'm running for Mayor because I want to seize that opportunity to transform the city.
I know that Londoners themselves are the best resource we have for fixing inequalities in the capital, and making it the world's first gender equal city - I've been out and about meeting them.
I've met young entrepreneurs who are using tech to work flexibly so their staff have a better work/life balance. (The infrastructure they required to enable this took over a year to install - something I'll tackle so London's digital providers are quicker, and more agile.)
We discussed London's big skills shortage and the ways that WE can provide apprenticeships for young people to encourage them into STEM careers and to address the shortfall in young women taking up STEM careers.
I've also been talking to business leaders about addressing the shortfall of women in senior leadership. I've met board members and partners who know not having an equal number of women on boards and executive committees is damaging for their businesses' productivity. We discussed the use of quotas to fix this, and how we can change workplace practices so that everyone feels included.
I also met senior leaders in the finance and legal sector who are doing great work to put women forward. They told me about their 'path to success' programmes to develop young female talent, and unconscious bias training for senior leaders - a blueprint WE would use across all of London's top firms to make them truly diverse and successful.
London's business leaders and innovators understand that gender equality is not a 'women's issue' but a business imperative. They understand, as one of them put it, that "equality raises your game as an employer." They have read the reports showing that allowing women to achieve their full economic potential would add $28trillion to global GDP and an extra 10% to the UK economy by 2030.
But we have work to do.
London's gender pay gap is 23% - higher that the already unacceptable national average of 15%. While many firms understand the importance of transparency and parent-friendly policies, too many are too slow to implement them. Childcare costs in this city are a third higher than the rest of the UK and only a tiny percentage of fathers are taking up the government's shared parental leave policy because they worry about damage to their careers.
I will tackle unequal pay by working with businesses to introduce transparency and equal parenting leave. I will change the way we work in London by championing companies with equal pay and equal promotion opportunities and flexible working policies. I will help new parents share care by introducing equal parental leave and supporting dads to stay at home if they wish.
I will make childcare affordable and practical. Recently I visited a ground-breaking flexible work hub, where parents do business on the first floor while their children are cared for in the nursery downstairs. London will greatly benefit from more examples of innovative solutions to working parenthood.
I want to be clear that it's time we empower women to do business on the same terms as men - for the benefit of all of us.
The Women's Equality Party: WE mean business.