A conning tower cannot make a direct heavy-shell hit safe

Could an armoured conning tower keep its occupants safe from a direct battleship-calibre hit?

Not reliably. Shock and vibration could disable the occupants, and nearby follow-up hits could cause catastrophic damage.

Thick armour would not make a direct battleship-calibre hit safe for the people inside a conning tower. The impact would transmit severe vibration and shock through the structure. Occupants could be disabled even without a projectile entering the compartment. A subsequent shell landing nearby could turn the damaged command position into a catastrophic casualty, since protection involves more than a penetration calculation.