Henry de la Poer Beresford (1811-1859) who became 3rd Marquess of Waterford in 1826, died following a riding accident. A dashing and somewhat eccentric character, who enjoyed drunken pranks, he was a keen horseman and fox-hunter. In 1839 he attended the famous Eglinton Tournament wearing medieval armour. In 1842 he married Louisa Stuart, daughter of  the 1st Baron Stuart of Rothesay. Louisa's sister, Charlotte, married Charles John, Earl Canning, Governor-General of India. Both the Stuart sisters had been childhood friends of Marochetti's wife, Camille, when their father was British ambassador in Paris.

The tomb of the 3rd Marquess was commissioned from Marochetti by his widow, along with a bust of her husband in his Eglinton Tournament armour. Following his death, Louisa wrote to a friend on 14 April 1859, "God gave my weakness a melancholy pleasure in looking on my Waterford's face in death; not a mark had injured its calm and monumental beauty, and he looked like a sleeping knoght, so grand and so beautiful, a sweet smile on the features". Lady Waterford was an amateur artist of some accomplishment, who probably gave what assistance she could to the sculptor in performing his task. On 7 Nov. 1859 she wrote again to the same friend: "Some day i hope you will go on a pilgrimage to Clonegam Church to see what Marochetti is doing for me in bronze. The clay (ready for casting) is all I have seen: the figure was so fine, so noble, in the robes of the Knights of St. Patrick". (Augustus Hare, The Story of Two Noble Lives, being memorials of Charlotte Countes Canning and Louisa Marchionness of Waterford, London, 1893, vol.III, pp.25 and 76). Louisa Lady Waterford was also responsible for further monuments in Clonegam church, to other members of the family; the effigy of John, 4th Marquess of Waterford and the half-length effigy of John George de la Poer Beresford, Bishop of Armagh and Primate of Ireland. The full-length version of the Primate's tomb by Marochetti, is in Armagh Cathedral.