Jellicoe's fast-battleship thinking supplied the operational foundation, while Fisher favored something nearer a strengthened battlecruiser based on the Lion class. The early Invincibles were not built to stand in a battle line, and even the Lions, Queen Mary, and Tiger were risky choices for massed fleet action. The compromise mission was to give the Grand Fleet a squadron fast and powerful enough to check enemy battlecruisers while the main battle line closed. This requirement explains why the ships did not need the very highest conceivable speed to perform their planned tactical job.
Chapter · 8:15-13:38
The fast wing of the Grand Fleet
The class evolved into a fast, heavily armed wing intended to protect the Grand Fleet's end and prevent German battlecruisers from gaining a tactical crossing position.