On 11/10/2020 22:42, Nick Maclaren wrote:
I bought this a while back, and this is the first year it has flowered.
Its growth and foliage is exactly like a clematis, but its flower
isn't. What on earth did I buy?

https://imgur.com/a/ZWuOf7o
https://imgur.com/a/rcJCcNS

Apart from the lack of a saucer it seems to fit with Cobaea scandens.
The web is reluctant to disgorge images of species other than Cobaea
scandens and Penstemon cobaea, but Cobaea pringlei has a non-spreading
calyx. Your plant looks somewhat intermediate between Cobaea scandens
and Cobaea pringlei.

Wikipedia offers a list of 18 species.

--
SRH