21st President: Chester A Arthur, 1881
Net = 21 (Arthur was the 21st president)
King Arthur = Arthur
Theft = 881 = 1881 became president
Chest of an A = Chester A
A net (21) was what the thief used to take the sword away. King Arthur (Arthur) spotted it and shouted "Theft!" (881 = 1881) to raise the alarm.
Connect Arthur to Chester A
King Arthur (Arthur) always admired the tattoo on his chest of an A (Chester A).
NOTE: The way Mammoth Memory remembers Chester is to think Chester has a big chest.