Hi Gums,
I also wonder how AoA protection laws could have caused a climb as 'nuts suggests
I believe Alpha Floor was triggered (at a certain Alpha threshold). The thrust goes to TOGA power despite the TLs being somewhere else. With no side stick input, the aircraft will then maintain Alpha Prot angle of attack.
All that was required was a side stick input to maintain current FL and disengage Auto Thrust.
To protect against over speed, L1011 - 500 had RSB (recovery speed brake). Full speed brakes were automatically deployed and had to be manually stowed.
PFM.