Casimir - Louis - Victurnien de Rochechouart de Mortemart Casimir - Louis - Victurnien de Rochechouart de Mortemart ( 20 March 1787 , Paris – 1 January 1875 , Neauphle - le - Vieux ) , prince of Tonnay - Charente , then baron of Mortemart and of the Empire , 9th duke of Mortemart and peer of France ( 1814 ) , was a French soldier , diplomat and politician . In 1830 Charles X of France made him president of the Conseil des ministres . Life . He was the son of Victurnien - Jean - Baptiste de Rochechouart , duc de Mortemart ( 1752 – 1812 ) , and his second wife , and Adélaïde de Cossé - Brissac ( 1765 – 1820 ) , only daughter of Louis - Hercule - Timoléon de Cossé , duc de Brissac ( 1734 – 92 ) , and Adélaïde - Diane - Hortense - Délie Mancini ( herself daughter of the duc de Nivernais ) . He and his family left France in 1791 and Casimir grew up in England , returning to France with his mother in 1801 . Despite belonging to one of the old noble families of France , he backed the First French Empire , joining the " gendarmes d ' ordonnance " ( commanded by the count of Ségur ) in September 1803 . He moved to the 1st Dragoon Regiment on 10 February 1806 and took part in the campaigns in Prussia ( 1806 ) , Poland ( 1807 ) , Austria ( 1809 ) and Russia ( 1812 ) , fighting at Golymin ( 1806 ) , Pułtusk ( 1806 ) , Heilsberg and Friedland , where he proved his sang - froid and firmness unber fire by beating off Russian attacks . He was made a member of the Légion d ' Honneur on 1 October 1807 , a lieutenant in the 25th Dragoon Regiment and " aide - de - camp " to general Nansouty on 2 and 10 March 1809 . He finally became a captain in the 25th Dragoon Regiment on the following 26 July . He fought at Ratisbonne , Essling and and was made an officer of the ordinance on 12 February 1811 and put in charge of inspecting the coasts of Holland and Denmark . After his success there he rejoined Napoleon at Posen and took part in the 1812 campaign into Russia , during which he received the title of baron of the empire and a donation of 2 , 000 francs of revenue from Belgium . Surviving the disasters of the retreat from Moscow , the baron of Mortemart returned to France with his health ruined – he was thus unable to take part in the last events of the following campaign . He fought at and Hanau – his conduct at the latter gained him promotion to officer of the Légion d ' honneur on 30 November 1813 . He returned to France with the army . In the 1814 campaign in France he was put in charge of presenting Marie Louise with the allied colours captured at Champ - Aubert , Nangis and Montereau . He was one of the first to fall with Napoleon I . After the first Bourbon Restoration Louis XVIII made de Mortemart a peer of France on 4 June 1814 and captain - colonel of the Cent - Suisses de la Garde , a position also held by his maternal grandfather at the time of the French Revolution . He was also made a kight of the Order of Saint Louis on 25 August 1814 . On 20 March 1815 , after Napoleon ' s return from Elba , de Mortemart escorted the princes as far as Béthune , where the king ' s military household was licenced . Shortly afterwards he rejoined Louis XVIII at Ghent and returned to France with the king in July . He thus reorganised