Ice cream all round. Just what you need when you’re in a hot How2 studio, sweltering under the lights.

Vanilla flavour comes from these things – vanilla pods, which you can sometimes find in the spices section of the supermarket. This is a dried-out pod, with a leathery texture.

Dried-out it may be, but it smells very strongly (and rather pleasantly) of vanilla.

Now, vanilla pods are the seed pods of the vanilla orchid, a beautiful plant Gareth just happens to have with him. Which is a little unusual, because they originally came from Mexico.

Here’s what the seed pods look like on the orchid – rather like runner beans, actually.

Here’s the thing: the vanilla orchid needs insects to pollinate it so it can grow the seed pods and reproduce, just like most other plants. But it’s picky about which insects, and the only insect that does the job is a particular kind of Mexican bee. So it you grow the orchid anywhere else, you have to do the bee’s job yourself.

You have to collect the orchid’s pollen, and pollinate the flowers with a little brush or swab. It’s not hard, but it takes ages. And then you have to wait for the seed pods to grow, then harvest them and dry them out – it’s a hugely time-consuming process. The result? real vanilla is very, very expensive.

However, as Gail quite rightly points out, vanilla ice-cream is quite cheap. How can that be, if the vanilla is so costly?

The answer is simple, if unexpected: vanilla flavour isn’t usually made from vanilla pods. It’s made from wood. Well, not lumps of wood like this, but wood pulp – a byproduct of the paper industry. You see, most wood contains a compound called vanillin.

And it’s vanillin that gives vanilla its distinctive flavour – so vanilla flavour made by extracting vanillin from wood pulp tastes very similar to real vanilla. And it’s an awful lot cheaper.

You’ll find more about vanillin at Wikipedia, and some history and chemistry at this site.