In message , Ernest Major
writes
On 19/05/2020 16:10, Ian Jackson wrote:
This has been growing for some time in the 'wild' part of my garden
(photo here):
https://ibb.co/TgtjQj7
It's presently around 4' 6" tall, and looks like a dark green spiky
thistle. However, there is no sign of any of the usual thistle seed
heads. Can anyone tell me what it really is?

Possibly woolly thistle (Cirsium eriophorum), which is the one with the
spiny particularly 3-dimensional leaves. Are you on limestone?

Yes - definitely limestone (Chiltern area). The garden's all clay soil
and lumps of flint. Thanks for the likely ID. [See my other post
regarding the leaves.]
--
Ian