From the Story
"Sir Cadogan's portrait stands alone in a corridor on the way to North Tower."
Discovered in Book 3, Chapter 6, Talons and Tea Leaves
"The short, squat knight is a loud, boisterous character, who challenges Harry, Ron and Hermione with his sword when he thinks they are laughing at him. When they ask him for directions to North Tower, Sir Cadogan leaps at the chance to go on a quest. He shows them the way, running through several portraits on his route to the Divination classroom."
Discovered in Book 3, Chapter 9, Grim Defeat
"Sir Cadogan's portrait is used as a temporary replacement for the Gryffindor common room entrance, whilst the portrait of the Fat Lady is being repaired. Sir Cadogan spends much of his time challenging people to duels, and the rest thinking up impossible passwords, which he changes at least twice a day. Although many students are irritated by Sir Cadogan, they cannot replace him, as he was the only portrait brave enough to volunteer for the job."
Discovered in Book 3, Chapter 13, Gryffindor Versus Ravenclaw
"Sir Cadogan proudly tells Professor McGonagall that he has just let a man into Gryffindor Tower. He tells her that he did so because the man had the week's passwords written down on a little piece of paper."
Before the wizarding community was forced into hiding, it was not unusual for a wizard to live in the Muggle community and hold down what we would now think of as a Muggle job.
It is widely believed in wizarding circles that Sir Cadogan was one of the famous Knights of the Round Table, albeit a little-known one, and that he achieved this position through his friendship with Merlin. He has certainly been excised from all Muggle volumes of King Arthur’s story, but wizarding versions of the tales include Sir Cadogan alongside Sir Lancelot, Sir Bedivere and Sir Percivale. These tales reveal him to be hot-headed and peppery, and brave to the point of foolhardiness, but a good man in a corner.
Sir Cadogan’s most famous encounter was with the Wyvern of Wye, a dragonish creature that was terrorizing the West Country. At their first encounter, the beast ate Sir Cadogan’s handsome steed, bit his wand in half and melted his sword and visor. Unable to see through the steam rising from his melting helmet, Sir Cadogan barely escaped with his life. However, rather than running away, he staggered into a nearby meadow, grabbed a small, fat pony grazing there, leapt upon it and galloped back towards the wyvern with nothing but his broken wand in his hand, prepared to meet a valiant death. The creature lowered its fearsome head to swallow Sir Cadogan and the pony whole, but the splintered and misfiring wand pierced its tongue, igniting the gassy fumes rising from its stomach and causing the wyvern to explode.
Elderly witches and wizards still use the saying ‘I’ll take Cadogan’s pony’ to mean, ‘I’ll salvage the best I can from a tricky situation’.
Sir Cadogan’s portrait, which hangs on the seventh floor of Hogwarts Castle, shows him with the pony he rode forever more (which, understandably perhaps, never much liked him) and accurately depicts his hot temper, his love of a foolhardy challenge and his determination to beat the enemy, come what may.