Lord Yarmouth sat as a Member of Parliament (MP) for Orford in Suffolk (which town was situated within his Sudbourne estate) from 1797 to 1802,[1] for Lisburn from 1802 to 1812,[2] for Antrim from 1812 to 1818[3] and for Camelford from 1820 to 1822.

Sir Richard Wallace erected a monument to his grandmother Maria Fagnani in Sudbourne Church, in the form of the stained glass east window, depicting Mary Magdalene, "the prostitute who washed Jesus’s feet with oil but was also the first person to witness the resurrection", seemingly "an intentional reference to Mie-Mie’s circumstances".

[19] By Maria Fagnani he had three children: In Hertford's last years the mental instability which had afflicted several members of his family became noticeable[22] and he is said to have lived with a retinue of prostitutes.

The diarist Charles Greville stated of him "there has been, so far as I know, no such example of undisguised debauchery" and described him as broken with infirmities and unable to speak due to paralysis of the tongue.

Thackeray's illustration of the Marquis for issue 11 was considered to bear such a resemblance to Hertford that threat of prosecution for libel effectively suppressed its publication.