Brian Oates has spent 30 years developing a technique for commercial wasabi farming.

It is notoriously hard to grow: it’s difficult to germinate, must be grown in running water, dies if over-watered, and is prone to disease when grown in bulk. It also sells for £160/kg.

Also you’ve probably never tried it:

The first thing to know about wasabi – or Wasabia japonica, as it’s officially known – is that you have probably never tried the real thing.

That light green paste nestled next to the pink ginger in your box of sushi? It is most likely a mix of mustard, European horseradish, and food colouring.

In fact, by some estimates, only 5% of the wasabi served in Japanese restaurants around the world comes from the rhizome, or root, of a wasabi plant.