Greatcoat
A greatcoat was a type of overcoat, especially associated on Earth with the First and Second World Wars. Such coats were almost exclusively worn by men. They easily fit over even full dress uniforms. Typically made of a heavy fabric, such as woll, they extended down to the mid-calf, so as to provide warmth over almost the entire body. They were distinguished by this exceptional length, prominent pockets, substantial collars and large buttons. Typically, greatcoats also had a strip of cloth with decorative buttons on the back, at roughly waist level. This strap across the back naturally gathered the cloth across the back to provide a characteristic pleat.
The Second Doctor, Jamie McCrimmon and Zoe Heriot, along with several resistance members, temporarily donned greatcoats as a disguise to escape from the War Lord's central headquarters. (DW: The War Games) Much later, when in his eighth incarnation, The Doctor once again wore a greatcoat — this time as a replacement for his own, destroyed clothing. (EDA: The Slow Empire)
Likely one of the more famous greatcoats in history, however, was that of Jack Harkness. Adopted when the Time Agent tried to perpetrate a con in the middle of the London Blitz, Harkness would go on to wear the coat — or at least others like it — for the many long centuries after he became effectively immortal. (DW: The Empty Child and others; TW: all episodes)
