Flying back into Heathrow last week (I had been in the US doing trade promotion), I was confronted with the possible dual delight of being diverted to another airport, and of meeting climate change campaigner and actress Emma Thompson in the passport queue.

Emma Thompson, flying over 5,000 miles to join the Extinction Rebellion protests in central London, has been criticised with rank hypocrisy as she burns goodness knows how many tons of carbon to campaign against, well, burning tons of carbon unnecessarily.

But I am sure she didn’t use the single use plastic toothbrush given away free to business and first class travellers.

It’s easy to ridicule her, and many do. But I have no doubt of her sincerity in her cause.

Climate change is happening, irrespective of your views on how it is coming about. And human activity is stunningly wasteful. Even climate change deniers accept human activity is just plain dirty.

Emma Thompson’s confusion between her clear and virtuous aspirations for a cleaner, healthier planet, and her actual behaviour is not unique. I see this the whole time.

People who proclaim themselves climate warriors yet drive gas guzzling cars, go on frequent foreign holidays, or work in industries that are less than environmentally friendly.

They can be lazy, saying that it is the job of the government to take action, yet taking little action themselves.

Margaret Thatcher, in a speech to the UN general assembly on November 8, 1989, made the case that human activity causes climate change. She was one of the first leaders to make such a speech and it was her that recognised incentivising markets for behavioural outcomes makes the difference.

She brought about tax discounts to unleaded fuel and now no-one drives cars running leaded petrol. Government action continues to this day, with carbon levies, plastics bans and incentives for recycling.

But when a government imposes a carbon levy, many wail about fuel poverty. The actions that meet middle class climate expectations may bear the heaviest burdens on the poor.

If you truly want to take action against climate change, do it. Stop, for example, buying out of season fruit, vegetables and flowers flown in from Africa. Refuse to buy plastic packaged food. Don’t fly on holiday and do buy a small car.

Every citizen can make a difference if they really want to. It’s not just up to the government.