"Cat(h)" writes

Broad beans

It is my first ever time planting those, and even my Dad never did, so
I have absolutely no idea of what to expect.
The plants are extremely healthy and vigorous looking, about 40 to 50
cm tall, full of white flowers with a black dot.

Yes, that's a normal broad bean flower.

I have noticed that
the flowers which come to the end of their lives are turning what to me
looks like a worrying looking sutty black. Yet again, I checked my
trusty Hessayon and its botanic hypochondria-inducing list of ailments
for peas and beans - nothing about blackening flowers.
Is that normal, and am I worrying over nothing?

It's normal. They go black as they die,
--
Kay