"Walterius comes" donated property "prope nostrum castellum…Medanta" to "Carnotensi monasterio Sancti Petri", for the soul of "coniugis mee Adelidis filiorumque meorum", by charter to , signed by "Walterii comitis, Rodulfi filii eius, Drogonis filii eius…".
He succeeded his father as Comte de Mantes. Comte d'Amiens. "Droco comes Ambianensium" donated property to "Sancti Petri Gismoensis" by undated charter, signed by "Droconis comitis, Eotde comitissæ, Falconis fratris comitis, Rodulfi filiii comitis, Gualterii alterius filii…".
He accompanied Robert II Duke of Normandy to Jerusalem and died on the journey. According to Orderic Vitalis, Henri I King of France took back the Vexin after the death of Comte Drogo. The necrology of Reims Saint-Rémi records the death "X Kal Aug" of "Drogo comes". 1