Battleships in Convoys?

[K-61]

I really have to wonder at the reasoning for placing battleships and other fast heavy warships into convoy columns and then sailing them slow enough to easily nail? I know that the Allies sometimes sent a battleship or cruiser type vessel along with convoys, but I have a hard time believing that they would sail inside the convoy at the slow pace of a convoy when they could sail much faster outside the convoy and be much harder to target. Has anybody actually read anything about this aspect of the Battle of the Atlantic? It just doesn't seem logical to me; a battleship has a much higher chance of survival at speed. I've sunk two battleships in two patrols in '39; at this pace the Royal Navy will soon run out of capital ships.