Quotes from rudderrudderrat:
"I believe Alpha Floor was triggered (at a certain Alpha threshold)." Yes, the AAIB thinks it probable because the captain saw a PFD message starting with "Alpha...". They also said that Alpha Prot was (briefly?) exceeded, which - as HN39 says - would be necessary for Alpha Floor.
"With no side stick input, the aircraft will then maintain Alpha Prot angle of attack." Quite. Re my question in a previous post, I've recently "gone to specsavers" and found the criteria for Alpha Prot disengagement on the A340 clearly stated
in the AAIB Bulletin:
Sidestick forward more than 1 second
OR
Sidestick more than half forward.