But occasionally, I go somewhere and find not just stories

but a really good storyteller.

In the grounds of Alnwick Castle, in the north of England,

is Alnwick Garden.

It's not quite as old as the castle,

that's been here about 900 years or so,

but it is just as impressive.

Inside is one of the world's largest wooden treehouses,

beautiful water features and also... this.

The slightly less conventional Alnwick Poison Garden.

Welcome to the Poison Garden.

All the plants in here have the ability to kill you,

so you're not allowed to touch or smell or stand too close to them.

This is Ricinus communis

and you can see that it has very architectural leaves,

but the issue with it is

that you can, under laboratory environments, take out ricin.

Ricin is the deadliest poison known to man.

Here we have Atropa belladonna, deadly nightshade,

a native plant to the UK.

These flowers that you can see here

will produce a black grape-like berry.

Four of those berries are enough to kill a child.

Very toxic indeed.

In Italy, especially around Venice,

the ladies used to squeeze the berries to get the juice

and then use the juice to put in their eyes

to dilate their pupils to make them look more attractive to gentlemen.

Because it's toxic, slowly you start to lose your vision.

What you do for vanity.

Ruta graveolens, again, a very common plant

that you can actually buy from garden centres, yet it is phototoxic

which means that if you get the sap onto your hands,

then in bright sunlight your skin will start to blister.

Once that chemical is in your system,

it will stay in that system for up to seven years.

Now, we had a senior gardener who came into the Poison Garden

and happened to see a weed growing out of this plant,

so without putting her gloves on she took the weed out.

Within an hour, she started to form blisters on her hand

and she ended up with third degree burns.

This plant is called Aconitum napellus.

It's very common.

It's often called monkshood.

The whole of the plant is very toxic.

Two years ago, there was a head gardener down in Surrey

who unfortunately was working with this plant

and he died a few days later,

and they put that down to the toxins from the plant.

Here we have a very common plant again.

This is laurel, used often as hedging.

The issue with laurel is that it will produce cyanide

and in fact, Victorians used to use leaves of these plants.

Cut in two, popped in a jam-jar with the butterflies that they'd captured,

screw on the lid and the butterfly would die naturally

because of the cyanide poisoning.

Now, this plant you can buy from garden centres,

a very common pot plant, it's called Brugmansia

and the whole of the plant is toxic.

It's often called the Angel's Trumpet.

It's an hallucinogenic plant so you can use it in all sorts of ways.

In fact, Victorian ladies would grow the Brugmansia on their tea tables

and then invite ladies around for afternoon tea.

What they would then do is in the tea pot,

shake some of the pollen which would go into the tea

and then the ladies would to start to loosen their tongue slightly

and talk about all sorts of nonsense.

We have a licence from the Home Office to grow cannabis.

So we have it here in a cage.

Obviously, it's a Class C drug.

We use this plant to start to introduce to children

all about the harmful effects of drugs.

This is Henbane.

It produces very peculiar flowers

that give off a very pungent scent.

The scent is so strong that often here we get people collapsing,

that's why we've got the bench next to the wall.

Mandragora, or Mandrake as it's commonly known,

a very popular plant now because of the Harry Potter phenomenon.

The whole of the plant is poisonous.

Historically, people used to think that there was a live little man

underneath the plant, because if you dug the plant up,

the actual tap root would often have two little legs and a little arm

and so people imagined that it was the devil himself.

Often people said they could hear the plant screaming as it was pulled up,

and so a lot of myth and legend grew up around the Mandrake.

The Duchess of Northumberland is the inspiration of the whole of this garden.

When she became Duchess, she had a vision

to create a modern, contemporary garden that would educate visitors.

So the Duchess then realised: children especially don't want to listen

to talks on herb gardens because they switch off.

If you can tell them that the plants are actually poisonous

and have the ability to kill you,

then you have the imagination of that child.

Thank you very much to all the team at Alnwick Garden, and to Trevor in particular!

If you want to know more about the gardens or the castle,

pull down the description.