Politics is about ideas, movements and moments. But it is always about people – about political leaders. Caroline Lucas has been, and will continue to be, an inspiring political leader who has been hugely influential both for UK politics and for Compass’ own 20-year history.

Today she has announced she is standing down as MP for Brighton Pavilion, having represented the seat since 2010. She was the first Green MP, but she must not be the last.

Caroline exemplifies the best characteristics of political leadership: bold and determined, and also kind, thoughtful and caring. She has often been a lone but bright light in Parliament.

She is the progressive leader everyone wanted but only the Greens were lucky enough to have.

It was Caroline that was in our minds when Compass members voted in 2011 to stop being just a Labour-focused organisation and asked Greens, Liberal Democrats and people of all parties and none to join us on the journey to a good society. How could we exclude her whilst including others who never shared our dreams?

There are two issues of disproportion when it comes to Caroline standing down.

The first is the disproportional influence one woman has had on progressive politics. She should be as proud of herself as we are of her.

But second is the outrageous fact that the Greens won 850,000 votes at the last election but only got one MP – Caroline. By contrast, it took on average just 38,000 votes to return a Conservative MP.

This is grotesquely unfair, not just to the Greens but to the country. When the voting system blocks these voices, we are robbed of the talent, the creativity, and the diversity we need to deal with the perma-crisis we face.

Our political and democratic system is broken. It hordes power at the centre, it opens itself up for the rich and powerful as it turns its back on the rest of us. It lets small factions win control of parties and ruthlessly exploit their position with impunity. It now produces identikit MPs who meekly follow the whip in a system that puts party before country.

By being one of the few exceptions to the rule, Caroline Lucas has consistently shown us that politics and politicians can be better. They must be better.

Hard on the heels of losing both Jamie Driscoll and Beth Winter from the future of the Labour Party, Caroline’s announcement feels all the more impactful.

In all the challenges and opportunities rapidly appearing before us, we need more leaders like Caroline, not fewer. That is why we need proportional representation.

As brilliant as she has been, and will continue to be, one person can’t fix a broken system alone.

Yet now, everywhere, people are picking up the torch; the overwhelming majority of Labour members and unions who know we need PR, the thousands of activists and millions of voters who campaigned and voted tactically in the May local elections, the huge number of people on the streets for XR.

From climate to poverty, from civil liberties to immigration, from housing to workers’ rights, the penny is dropping: we can’t build a better society on a broken political system.

Better politics looks like Caroline Lucas. We know what to do – she has shown us.

Everywhere change is in the air. We always said it would be a pitch invasion. Big change never comes from within the system.

Write to your MP to demand a new politics today – starting with PR.