If a Banksy appeared on your house, you'd be sitting on a fortune, right?

At first you think you're gifted, but you're actually not.

This is a tale of two murals, Margate's Valentine's Day Mascara and the lowest off seagull.

And the true cost of free art for the people who have to live with it.

40,000 pounds cost per annum.

We didn't know what to do.

Nobody's turned up to say, we'll help you protect it.

The Banksy story.

When Banksy comes to town, listen on BBC Sounds.

Hello and thank you for downloading the more or less podcast, with a program that

delights in data, marvels at maths and swoons over statistics. And as ever, I'm Tim Harford.

Here at more or less, we are constantly fact-checking wild claims, but proof can be a strangely difficult beast to capture.

Sometimes you don't have enough data, sometimes it seems to be a matter of opinion, and

sometimes, just sometimes, the proof of the pudding is in the eating. Every day we use a toolkit

of known proofs to try and answer our listeners' questions.

But who do we have to thank for this toolkit, and how did they set about proving the unknown?

Luckily for me, Adam Kutjarski has just written a book about this very topic called Proof,

The Uncertain Science of Certainty.

Adam is a mathematician and professor of epidemiology at the London School of Hygiene and Tropical Medicine. I sat down with him to hear more about some of the

proof pioneers included in his book. We start in the lead-up to D-Day in 1944.

Here on what we get to be the eve of the greatest military operation of all time. The Allies were trying to predict what the Germans might have waiting for them in occupied France,

and in particular a fearsome new tank called the Panther Mark 5.

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