To make the best of a bad situation.
The brave but foolhardy knight Sir Cadogan once got into a tricky situation with a "dragonish" beast called the Wyvern of Wye. It swallowed his horse, melted his visor and sword, and broke his wand. But brave Sir Cadogan found a fat gray pony and charged back towards the fierce creature, splitting its tongue with his broken wand, and causing the beast to explode (Pm). He kept the pony, and it's the very one shown in his portrait at Hogwarts. When wizards say "I’ll take Cadogan’s pony" they mean to make the best of a horrible situation (Pm).
Historical reference, circa 1000 AD. The phrase is most often used by elderly witches and wizards (Pm).
Tags: culture (Wizard)