Scharnhorst and Gneisenau illustrate the problem of attacking a convoy escorted by an older battleship. One raider could try to draw the escort away while the other approached the convoy. The escort's answer was to remain with the merchant ships, since it could not catch the faster raiders. It could also report their position and bring faster Allied forces towards the encounter. King George V and Ark Royal are examples of the forces a raider would then risk attracting.
Notable Point · 7:38-8:49
Why a convoy escort should resist a raider's decoy
A Revenge-class battleship could protect its convoy by refusing to chase one German raider while the other approached the merchant ships.