[bikerjohn]

Purple sprouting broccoli, about one foot high at present.  White powdery lumps on underside of leaves, and, to a lesser degree on top, turning to brown spots where the white has been.  Any ideas please?
Many thanks, John. :roll:

[richyrich7]

Sounds like white blister sometimes called white rust, remove infected leaves don't compost them.
I believe it's a mould, down to the damp weather.

[bikerjohn]

That looks exactly like it, many thanks.
\john.