Been there!
August '85 over the Channel in murk from 1000' to FL impossible. Vectored for an inbound at 10,000' and Freddie rolled me out 1/2 mile astern but I didn't have any radar contact - which was unusual even for me! Closed to 1/4 mile in cloud without contact, so assumed the D had got the height wrong and that the bogey was actually at low level below the crud.
Aggressively lowered the nose and started a fast descent, whilst desperately bogling the scope for a return. Completely lost SA and broke cloud below 1000', 40 degrees nose down at c480 kts. Immediately snatched a load of G and induced a high-speed stall. Relaxed slightly into light wing-rock and watched in horror as the horizon came up around my ears and the altimeter kept spinning down. I clearly remember it bottoming out some 50' below zero before starting to climb again. Luckily the HUD camera wasn't running, so I will never know how low I actually was.
The aircraft was a bit bent (+9G) but the tanks and flaps stayed on and I managed to calm the heartbeat down enough to land back onboard. Still gives me the shivers.
Disorientation is still a killer.
Mog