Thanks for that suggestion Mike - had considered that amongst many other things but decided no. Although it continued to grow, and take over the pot to the detriment of the other plants, it never looked likely to produce any terminal flowers, just those I described close to the stem and on the laterals. My first thought was a type of Mercury but that also proved no. In the end I turfed it out and forgot all about it until reading your post😊Perhaps one day I shall see a photo that reminds me again and will say 'Ah, that was that plant that I couldn't identify!'
Nice to have you active on the Forum after a while 😊