Henbane

It's use in brewing, in Germany, was banned in 1516

 

Mandrake although perennial is not frost hardy so you will need to protect over winter.

 

Aconites are probably more toxic and better looking.

 

Wow! That's amazing. I love Germany.

Any info on wolfsbane?

 

Wolfsbane, so called as that was what it was used for, various Aconitum species also called Monkshood, Leopards bane, Devil's Helmet, typically blue flowered although Yellow species are known and there are white forms, some are climbers. All parts of all species are highly toxic.
Hardy, easy to grow from seed.

 

Might give it a try. Growing it that is.

 

Herb Seeds Herb Mandrake officinarum

Or you might be able to persuade them to send you one even though they apparently do collection only: Mandragora officinarum

And this one is interactive!

I think Mandrake is more interesting to Harry Potter fans than gardeners, looks a bit boring for the trouble I think.

Have you visited Alnwick Poison Garden @Adam422 ? It's very well done and the tours are great

 

Thanks for the info mate. Will try them.