Note 209 — Chapter VII · THE PERIOD OF TRANSITION: CYLINDRICAL TOWER-KEEPS
Reading edition
E. Lefèvre-Pontalis, Le Château de Coucy, pp. 48, 49, shows that the donjon forms part of the latest work undertaken by Enguerrand III., lord of Coucy, the founder of the present castle, who died in 1242: it was evidently completed about 1240.