Sam was lying in bed one morning when her tenant in a house she owned in Margate sent her a photo of a piece of graffiti that had appeared on the wall outside.

Astonishingly, it looked like a Banksy. It would turn out to be perhaps the graffiti artist's most interesting new artwork of recent years, Valentine's Day Mascara (pictured above), which was revealed in Margate on Valentine's Day, 2023.

Bamboozled, Sam googled: what do you do when you wake up with a Banksy on your wall?

"What did Google say about that?" I asked her.

"Nothing! And I was like, I need to contact the council, I need to find an art gallery who can advise me."

Sam called Julian Usher at Red Eight Gallery. Julian's team, conscious that new Banksys are under immediate threat from street cleaners, the weather, rival graffiti artists and other art dealers, promised he'd be in Margate within the hour: "We knew we had to get the piece covered," say Julian.

And there was another reason Julian got to Margate double-quick: if Banksy chooses your wall for one of his drawings, you could be seriously in the money.

For the second season of my BBC Radio 4 podcast The Banksy Story, which is called When Banksy Comes To Town, I've been following the very different fates of two sets of homeowners who wake up one day to find a Banksy on their wall. The season shows just how important his graffiti becomes for a local community – and why people disagree so vehemently about what should happen after it's discovered.

Sam became the custodian of Valentine's Day Mascara, which speaks to the theme of domestic violence, incidents of which usually spike each Valentine's Day. It's a complicated bit of work. A peppy 50s housewife with a black eye has bludgeoned her partner. A real pan with flecks of red is at her feet, and his painted legs are upended into the real fridge-freezer that Banksy left by the wall. A broken plastic chair testifies to the fight they have........

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