We are in the fifth decade of the Women's Aid movement, working with survivors of domestic abuse, campaigning to protect their rights, and striving to make sure their voices are heard - in public and in politics. I am very proud to be chief executive of Women's Aid.
In all those years, progress has been made, sure - but many women are still denied safety even in their own homes, from the people they should trust the most.
There are many hundreds of thousands of men who still feel entitled to control every aspect of a woman's life, to diminish her, wipe out her self-esteem, treat her body as belonging to him in every way, and even to kill her - because in 2017 two women a week in this country are still being killed by their current or former intimate partner. The Femicide Census, which Women's Aid published at the end of 2016 in partnership with Karen Ingala Smith, found that between 2009 and 2015, 936 women were killed by men in England and Wales.
Misogyny and sexism give men permission to abuse. It's as simple as that. We all know Trump's locker room jokes aren't funny. But they aren't just crude - they are dangerous. They normalise sexism so that we accept it. We see it as how things are. And then we see men's violence against women as inevitable. That's just how it is, isn't it? In fact, when we were launching the Femicide Census, somebody commented on Twitter that 936 women being killed in seven years seemed "about right" and that it was around the same number of people who die each year after being hit by icicles in Russia (I wish I was joking).
I would love to believe that those attitudes that accept male violence as normal were dying. But after the past year, it's impossible to believe that. They are very much alive, and kicking. Misogyny is on the march, all the way to the White House.
So we march for optimism: we believe male violence against women is not inevitable. Men can stop, if they choose. They don't stop because it means giving up power - and Trump is showing men very clearly that power and misogyny go hand-in-hand. He's a simple guy, and it's a simple message.
So let me try and make it simple too. Misogyny puts women in danger. It kills. And it harms men too. Inequality eats away at trust. It means women don't trust men's motives; they cross the street because they fear them. Bitter experience makes women wary, they are resentful of men. Or they resort to laughter, but it's laughter with an edge - men can feel it. Is this what we want for our relationships, for our futures? Mistrust and misunderstanding, with domestic abuse appallingly common? Or would we rather work together, women and men, to change the record at last?
Thousands of women in the UK, right now, are denied the basic human right of safety in their own homes. They are robbed of their autonomy. They and their children are thrown in harm's way, again and again, by systems that should protect them but instead let them down.
This is happening because when sexism asserts itself, not enough people say no. And then women are robbed of the power to say no. Well, we have that power and we are using it. That's why I march.
Polly Neate is chief executive of Women's Aid. For more information on the Women's March London, visit the website here