[3] They had four sons, including:[1] In 1769, Lady Grosvenor was discovered in flagrante delicto with the Duke of Cumberland, brother of King George III.

Their affair became a national scandal when her husband sued the duke on the grounds of 'criminal conversation' with his wife, and the lovers' correspondence was published in the press as part of the trial reports.

[4] Lady Grosvenor prevented the baron from securing a divorce on the grounds of her adultery by gathering evidence of his own extensive sexual misconduct, personally 'going into bawdy houses [...] to search and procure witnesses'.

[4] The diarist and artist Joseph Farington dubbed Lord Grosvenor as 'one of the most profligate men of his age, in what relates to women'.

[3] This wealth of evidence meant that the baron could not be granted an annulment, and was obliged to support his wife for the rest of his life.