I recall the "ramshorn" effect. Because the roots of a swept wing stall last and because the centre of lift moves forward as it travels towards the root then the nose pitches up (as mentioned before in this thread). In addition (this is the deep stall bit), the unstalled air flow is effectively channelled straight down (remember that downwash is an attribute of lift) onto the top of the tailplane, pushing it down, causing the nose to pitch up further. The problem gets worse the deeper into the stall the a/c goes, hence the deep/super stall with swept wing and no T-tail.