We are at a crossroads.

Trust in politics is low, and people are right to feel let down. The economy works beautifully for those at the top and barely at all for everyone else. Across the West, that frustration is being picked up by people who offer someone to blame rather than something to fix.

Liberals can offer something better. It’s in our DNA, but sometimes we get confused about what liberalism is and fail to make the case.

So let’s say it plainly. Liberalism has one founding fight, and we have fought it in every century – the fight against power piled up in too few hands. We took on kings. We took on the established church. We broke up monopolies and old boys’ networks. Wherever power gathered in a small group, liberals were the ones who said: spread it out.

Now look at where power is gathering today.

Since 1989, the wealth of the 200 richest families in Britain has grown from £42 billion to £711 billion. Over the very same years, the public wealth of the country fell from a positive £337 billion to minus £1 trillion. Their fortunes grew more than three times as fast as the economy as a whole. That is not a story about clever people doing well. It is a story about power collecting in fewer and fewer hands while the rest of the country goes backwards. A liberal who shrugs at that has forgotten what liberalism is.

This is why a wealth tax is not a borrowed socialist idea. It is a liberal one. Free markets need power to be spread out. When wealth piles up at the top it stops being money and starts being influence: over the press, over politics, over the rules the rest of us have to live by. Concentrated wealth is bad for markets, bad for democracy, and bad for the simple liberal promise that where you end up should depend on what you do, not on who your grandparents were.

This is the bit that everyone knows but the mainstream parties rarely say: The very richest can end up paying a smaller share than the people who clean their homes. This is not a free market rewarding effort. This is a system tilted towards those who already have the most.

A small tax on very large fortunes would begin to put that right. Something like a penny or two in the pound, each year, on wealth above ten million pounds. It would touch only a few thousand people. It would raise more than ten billion pounds a year, real money for the things we all rely on. And it would start, gently, to turn the tide on a forty-year drift towards the top.

Now, you will be told it cannot be done.

You will hear a lot of clever, careful, reasonable-sounding objections from nice people. Be a little suspicious of any argument that, step by careful step, always arrives at exactly the same place: leave the people at the very top precisely as they are.

They will say the rich will simply leave. But you cannot pack a London street into a suitcase, and most great fortunes are tied up in land, homes and businesses that trade here. We can also treat someone who has lived here for years as a resident for tax for years after they go.

They will say it is too hard to work out what people own. Shares and bonds are valued every single day. The harder cases, a private firm or a painting, can be handled with sensible rules and by letting people pay over time or valuing it at the point of sale.

They will say it raises too little to bother with. More than ten billion a year is not too little. And the money was never the whole point. The point is the power.

They will say it has been tried before and dropped. The old versions were badly built. They set the bar too low, so they hit the wrong people, and they were so full of holes that the genuinely rich slipped straight through. We know how to build it better now. So let us build it clean: a high starting point, a low rate, and no exemptions.

And some will say, very reasonably, tax them another way instead. We can certainly reform other taxes too. But most of those routes miss the shares and the companies where the biggest fortunes actually sit. They ask the comfortable middle to pay a bit more while leaving the very top largely untouched. That is not the same thing at all.

This is the opportunity in front of us. This is the crossroads.

Britain could be the country that shows this can be done. That a free, open, enterprising economy can also be a fair one. That you can take on concentrated power without tearing down liberty, and come out stronger for it.

This is a liberal example worth setting. Let’s set it.

* Tom Reeve is a Liberal Democrat councillor in Kingston upon Thames