Spanned figures in multi-column layouts

[Steve Rickaby]

I am struggling to find a way to make an anchored frame span more than one column of a multi-column layout. If I set the frame uncropped, it messes with the text flow (the text threads to adjacent columns above the figure, which is not what I want), and if I set it cropped, half of it disappears behind the adjacent column of text. If I create a  paragraph for the anchor that has 'across all columns' set, I get the same effect as setting the frame uncropped.

I suspect it might be something to do with the runaround properties of the frame, but I seem to remember that this can only be accessed using Dark Magic. Can anyone suggest a solution? What I want to achieve is for a figure to span more than one column, but for the text threading to be unaffected by the presence of the figure.

-- 
Steve