It's a datura, Angels trumpet. If you intend to keep it, You may need to protect it, even inside your greenhouse. If not collect the seeds from the prickly seed head, dry and re sow next spring.
There will be others who will know more of which variety etc.

This question wins the prize as the most frequently asked this year!

That's a Datura stramonium, and all parts are toxic. They seem to be appearing in gardens all over the UK! Up to you if you like it, but the general opinion seems to be to bin it.

The only reason to 'bin it' is if you don't want it in your garden because you didn't plant it.

There are plenty of plants in any garden of equivalent toxicity. Datura gets a bad name because people are daft enough to deliberately ingest it to get 'high'.

Good heavens, PG, well you live and learn as they say. I won't be trying that one though!
Spritzhenry - I disagree!! The one about how to get rid of antisocial cats crops up even more often, lol.

It would be interesting to be able to do a count, wouldn't it. We've had lots of questions about over-wintering dahlias, 'geraniums' and fuchsias, too. ;-)