Unknown flower at Hestercombe

Hello spritzhenry - lovely to meet you today at Hestercombe. I've been looking in my old RHS Plants and Flowers book and I reckon this could be Hibiscus trionum (p264 in my book).

Hi Stonewell! I'm glad you found us - isn't it a good site! Will check on your plant identification. Thanks for the message!

Looks like an Abelmoschus (Hibiscus) we grow here in Queensland.

I think it's hibiscus trionum as well. I've seen this growing naturalised in New Zealand (the botanists are undecided where it originates). Annual or short-lived perennial but pobably not hardy in the UK