The thick black tip to the tail along with the grayish proximal half to the undertail with just a hint of rufous to the inner edge of the inner web (quite an extreme pattern in fact) should be enough to clinch the id.
Edit: ok sorry I hadn’t seen there were 2 pages. I guess it’s much clearer with the second pic now!
very useful thread, thanks to all. Just to clarify 'just a hint of rufous' refers to under tail, but what about the secondaries: how reliable is the rufous panel on the wing (visible in the birdguides in Little and Blue-breasted but nowhere mentioned in the text)?
Thanks