How big's the pot? Has it been in the same one since 2016?

Bamboo,
Yes, but the pot is about 18" dia. and the plant sits in the middle with about 6" of space all around. It gets fed. and grows a lot of leaves.

Stop feeding it and it should then produce flowers. over feeding usually causes leaf growth at the expense of flowers. There is a section on the RHS site for it have a look.

I have the same plant bought in the same year as yours and this is the first time it's flowered this year . I'd be patient maybe next year mines in a 9" pot 3ft high Inc pot they do seem to be slow growing.

Youngalistair
Sorry for delay in replying but have only just seen your reply to my question re Mathiasella. Gives me hope and I will persevere. Thank you.

Seaburngirl

I have only just seen your reply too and will do as you suggest and I will certainly have a look at the RHS site.
Thanks,