He was promoted lieutenant colonel on 15 March 1810, and served as assistant adjutant-general at Buçaco and Barrosa, directing a successful charge by a squadron of the 2nd Regiment of Hussars (KGL) against the French dragoons.

[3] He led the 12th Light Dragoons to disperse some of the broken French infantry after the Battle of Salamanca, and was wounded while covering the withdrawal from Burgos.

At the Battle of Waterloo, the 12th and 16th Light Dragoons were told to charge down the slope, but no further, to support the withdrawal of the Union Brigade of heavy cavalry.

A French lancer saw him move where he lay and stabbed him in the back with his lance, exclaiming "Tu n'es pas mort, coquin" (You're not dead, you rascal).

During the night after the battle, he was roughed up by a Prussian looking for plunder, and a mortally wounded soldier of the Royal Dragoons had crawled upon Ponsonby's legs and lay dying.

[8] Despite the quixotic nursing ideas of his sister,[further explanation needed] the notorious Lady Caroline Lamb,[9][10] and despite being further bled of 120 imperial fluid ounces (3.4 L) over two days, he managed to survive against the odds from his seven major wounds.

[citation needed] He left the governorship in May 1835 (but remained the de jure Governor until 30 September 1836), and was appointed colonel of the 86th Regiment of Foot on 4 December 1835.

[12] He died suddenly at an inn, The Wellesley Arms at Murrell Green near Basingstoke, on 11 January 1837 and was buried in the crypt of St Nicholas' Church, Hatherop, Gloucestershire.