It was the largest exercise of democracy in Britain’s long democratic history. On June 23, 2016, the people of the United Kingdom voted to leave the European Union. The best single reason for the U.K. to leave the European Union at the end of October is that this is what the British people voted to do.

It’s been a long time coming. Brexit was supposed to happen at the end of March. But the deadline has been extended twice, as the House of Commons rejected every possible approach to resolving the crisis.

The delays are unpopular, as demonstrated by recent election results. The governing Conservative Party suffered a smashing defeat in the local elections, while the European elections delivered a stunning victory for the new Brexit Party, which has as its only goal getting Britain out of the EU.

What has stopped many MPs from heeding the voters and supporting an immediate exit from the EU is fear that Britain will suffer economically if it leaves. Or, to put it more exactly, Conservative MPs are afraid that leaving the EU will damage their party’s reputation for economic competence — a reputation they see as key to defeating Jeremy Corbyn’s far-left Labour Party.

This fear is misplaced. EU membership is no guarantee of prosperity. Germany is prosperous, but Greece, also a member of the EU, has been immiserated. Inside or outside the EU, prosperity depends first and foremost on the wisdom of your national policies.

For Britain, the EU adds relatively little economic value. British exports of goods go disproportionately to the world outside the EU, so the EU’s common market is of less use to it. Unfortunately, the EU has never been able to create a truly common market in services, in which Britain dominates. And the UK imports a lot of food, which the EU makes more expensive.

Being in the EU means Britain gives preference to talent from Europe, a rich but small region, not talent from around the world. And the EU loves to regulate, which adds costs that Britain has to pay.

Of course, leaving the EU immediately is not going to be all smooth sailing. Britain cannot leave a trading and regulatory area it has been part of since 1973 without some bumps. But it is the government’s job to prepare for and to minimize those bumps.

The fact that people are still concerned about the bumps goes to show what a bad job the British government has done in its exit negotiations with the EU. It managed to work itself into a corner by not preparing fully for exiting without a deal, while the deal it did negotiate turned out to be a bad one.

But Britain still has time to redeem those mistakes. After Prime Minister Theresa May’s successor is chosen, the new government will have about three months to prepare for exiting the EU without a deal. It can also use that time to restart the negotiations with the EU.

If those negotiations produce a genuine free trade area between the EU and the U.K., that would be ideal. But the odds of such a success are very low. The EU likes the unacceptable deal it has already negotiated and has no desire to change it. Britain must be fully prepared to walk away in October.

The recent elections show what will happen if Britain extends the Brexit deadline again. Political parties are realigning, with every vote now a referendum on Brexit. Both the Conservative and the Labour parties are suffering as a result: the Conservatives because their supporters want Brexit, and Labour because its supporters have no idea what it wants.

Conservative MPs should recognize that the biggest peril facing their party is failing to finish the job voters gave them in 2016. And Labour MPs should recognize that they risk a wipeout, with working-class voters heading to the Brexit Party and the urban rich drifting to the rival Liberal Democrats.

The economic consequences of Brexit will be low in the short run, and positive in the long run. The Irish border problem can be solved if there is good will between Britain and Ireland, as there must be.

The greatest risk in Britain today is that the British people were told that the 2016 referendum was their chance to choose the destiny of their nation. Any economic risks attached to Brexit are nothing compared to the political risk of denying the people the voice they were promised.