The Brexit fanatics want you to believe there's no time to reverse things now. But it's not true

On Sunday, about 850 people will cram into the Cambridge Junction – a venue typically attended by musicians and their fans.

There won’t be a moshpit or any smashing of guitars on this occasion, but it will still be fairly raucous, with the attendees calling loudly for their right to have the final say on any Brexit deal.

This is the latest rally in the People’s Vote’s Summer of Action campaign. It will be the third at which I have spoken, after Bristol and Newcastle. Other rallies will take place in Cardiff, Liverpool and Birmingham, culminating in a huge event in London on 20 October.

The previous People’s Vote march on Parliament Square in June was a major milestone for the campaign – 100,000 met that balmy Saturday afternoon to demand they have that final say. Any vote would, of course, include the option of an exit from Brexit, which is vital given the mess that has been made of the negotiations.

What has been so important about these rallies is that they have proven Brexit is not inevitable.

When the Liberal Democrats first took up this campaign two years ago, one of the big problems we faced was a sense that Brexit was inevitable.

Over recent months it has become increasingly accepted that there is a way out through these democratic means. That’s why so much polling now shows growing support for a people’s vote, while significant research this month found there are now more constituencies in favour of remaining in the EU than leaving.

We’re a democracy and the people have the right to change their minds when they have been presented with the reality of what Brexit will mean: a slowing economy; food, medical, labour and – to be fair, no one predicted this – even sperm shortages.

Inevitability was the great weapon of the Brexit ideologues and they knew it. They recognise that we have neutralised this sense of “there’s nothing you can do now”. They will try whatever they can to restore that sense of inevitability.

This is why we are seeing claims that we have simply run out of time to legislate for a people’s vote before 29 March next year, the date that has been set for Britain to leave the EU.

But we haven’t run out of time.

The ideologues’ argument is partly based on the fact that primary legislation for the 2016 poll took seven months, including a long summer recess that would obviously not be a factor now.

The parliamentary timetable would be shortened dramatically given there is a pro-EU majority in the House of Lords that would most likely support a vote. Similarly, the number of supporters in the Commons is growing daily – what we need is for Jeremy Corbyn to come out in favour.

This would be the right position for him to take, given authoritative research from Queen Mary University has shown that 78 per cent of Labour members want the final say on any deal.

Ditto the SNP.

With a majority in both chambers, legislation could take weeks rather than months. After adhering to Electoral Commission advice and polling rules, the timetable is extremely tight but it is achievable.

Moreover, there is also the blindingly obvious move: extend Article 50.

There is no legal reason why we cannot do this. Article 50’s two-year exit timeframe was designed as a poison pill to make sure member countries were put off from leaving. What was not anticipated was the rise in anti-establishment feeling across the world that would lead to a country swallowing that pill.

Both the EU and British negotiating teams would welcome any extension given it is clear that such a big, complex secession cannot be achieved in just 24 months. I don’t believe there could ever be a deal as favourable to the UK as simply staying in the EU, but it has proved impossible to even achieve a half-baked solution in such a rush.

In short, where there is popular and political will, there is a way and we must not let the Brexiters fool us into thinking otherwise.

Brexit is not inevitable.

Sir Vince Cable is the leader of the Liberal Democrats and MP for Twickenham