IF failed Labour leader Jeremy Corbyn is yesterday’s man then his brother Piers is today’s man – and he’s in a certain amount of trouble.

Piers Corbyn is a meteorologist and notorious climate change denier, and it seems he has now emerged as an equally outspoken vaccination denier. He is behind leaflets distributed in London that liken the anti-coronavirus vaccination campaign to the Nazi concentration camps.

The leaflets bear a drawing of the entrance gates to Auschwitz where the slogan “Arbeit macht frei” has been changed to “Vaccines are safe path to freedom”. They claim that the vaccines contain nanochip technology which will allow their recipients to be tracked electronically.

The leaflets carry Piers Corbyn’s name and appear on his website. Southwark Council have reported him to the police. He’s not the only one. Hospital staff who arrive to vaccinate vulnerable people have been heckled by anti-vaxxers.

Now I don’t say that no-one should be allowed to defy the conventional wisdom, nor that all conspiracy theories are baseless. We should be allowed to question everything we’re told.

For instance I happen to think that Abdelbaset al-Megrahi, the man accused of the Lockerbie bombing, was the victim of a conspiracy himself, and was innocent. Dr Jim Swire, whose daughter Flora was one of the 270 people killed, doesn’t think Libya was even involved, and Hans Koechler, an observer at the trial, called al-Megrahi’s treatment “a spectacular miscarriage of justice”.

The only witness who linked al-Megrahi to the incident was a Maltese shopkeeper who was later found to have been paid to testify against him.

Many of those who have looked at it closely agree that al-Megrahi didn’t do it.

But where events are shocking or unexpected or cause anxiety or just bafflement, conspiracy theories always thrive, as people feel a need for explanations.

The deaths of Princess Diana and John F Kennedy and the terrorist attack on the World Trade Center were all baffling and unexpected, and so it wasn’t long before the conspiracy theories emerged – that Diana was murdered because she was carrying Dodi Fayed’s baby, or that anti-Castro Cubans had killed Kennedy, or that the Israelis were behind 9/11.

Maybe some conspiracy theories are only a bit of fun, best left to some crackpots to enjoy. You don’t have to look hard to find someone who’ll argue that the moon landings were faked or that Paul McCartney died in 1969 and a lookalike has been impersonating him ever since. If somebody believes that, it probably does no harm and is safe to ignore them.

But some conspiracies are highly dangerous and need to be tackled head-on. Leave them to gain a foothold and they can do untold damage. There are those Holocaust deniers who claim Hitler didn’t murder people in their millions, and the reports of it were all a ploy to win sympathy for the Jews.

How they explain the footage of piles of corpses and starving survivors, I’ll never know. But they give credence to Nazism.

There were also the cancer deniers. For years tobacco companies tried to undermine the evidence that cigarettes caused cancer. As long as people smoked and died, they’d make money.

And then there are the climate change deniers. Some, like Donald Trump, claim that it isn’t happening and it’s all a hoax. Slightly more observant ones accept that it is but claim it isn’t the fault of humans – as if setting fire to millions of tonnes of fossil fuels had no effect. They can undo all our best efforts at a stroke.

When I first came here I was impressed by how green Cumbria was, and not just its mountains and fields. There were gently swaying wind turbines and fortnightly recycling by Carlisle City Council. Other places I had lived didn’t do as much or as often.

Our nuclear power stations create nasty, dangerous substances that we aren’t sure how to dispose of. But at least they don’t emit carbon. And yet now we have plans to open another coal mine in the west of the county.

Those who are being called “vaccine hesitant” or more directly anti-vaxxers are endangering lives in the same way as the cancer deniers and climate change deniers.

But it’s always easier to stop people from taking action than to persuade them to take it. All the deniers have to do is sow a small seed of doubt and lazy people will be only too happy to latch on to it.