... this appeared in my garden, and while I admire it's vigour, I am a little worried that it may be a Triffid ... or something equally unwelcome.

If anyone knows what it is, I would really appreciate knowing whether to tend it, lovingly, admiring as I go, or - (as is more likely) - dig the perisher out quick, before it goes to seed and we all disappear in its progeny. Thank you.