Perhaps this shows it better.

The glossary in Mills & Barnes ('Amateur Gunsmithing') calls this an 'intercepting sear', so what are we really talking about here? A quick internet search shows liberal use of the term "intercepting safety sears", so they are the same thing? In that case, JPK, the above is a good illustration of an 'intercepting safety sear'!

BTW, here's a photo of the Purdey illustrated in Mills & Barnes: