Great, thanks everyone.
The F4 and Hunter pics were just what I needed, I was unsure as to whether there was one notch or a series of notches.
However, I’m still a bit confused, is it a low speed or a high speed design feature, or both? I thought that the increased span-wise flow on a swept wing encouraged a larger vortex at the tip, as such creating a large increase in induced drag (a low speed problem). Reducing the span wise flow would therefore reduce the induced drag.
Or does the vortex created by the tooth flow over the top of the wing energizing the boundary layer (like a vortex generator) and as such delay boundary layer separation that occurs in the transonic region?
I guess it makes sense that it does both, does it? Or have I got it all wrong?
SW