I'd never heard of this plant until my neighbours cut one down and were going to thrown the remains in the bin. It was cut down because apparently it had never flowered. On investigation it seems the Moonflower is a species of night-blooming Morning Glory, native to tropical and subtropical regions of North and South America, so it's not surprising it didn't like being in southern England :-))

Anyway, before it went in the bin, I snipped off two seed pods, one of which I cut in half and this photo is what it looks like, inside and out. This is about twice life size.

In the PiP is an even closer shot of the seeds. Thanks for looking.