These letters are written by Lord Duncannon in his role as Chief Secretary for Ireland and as an MP for Great Britain (Derby and Saltash) and Ireland (Kilkenny). He writes to the 3rd Duke (his father-in-law) and Lord Hartington (his brother-in-law) concerning mostly Irish political affairs which the 3rd Duke and Lord Hartington oversaw in their roles as Lord Lieutenants of Ireland between 1737-44 (3rd Duke) and 1755-57 (Lord Hartington). He writes also of foreign affairs such as the threat of invasion from the French and conflict with French fleets near North America as well as battles in Flanders and Spain and the Jacobite uprising in Scotland. He mentions the Houses of Parliament in England and events that transpire there. There is minor mention made of personal affairs such as the health of Lady Caroline (his wife), his children and their wider shared family.
In his letters to the 3rd Duke, Lord Duncannon writes of commands he has carried out on the 3rd Duke's behalf, political affairs that require the Duke's input and reports from people with whom he has communicated regarding home and foreign affairs.
Topics include: the Duke of Newcastle; Committee of council meeting about bills; the bill for the encouragement of raising flax seed in Ireland; the cabinet council; recommendations for commissions and vacant posts; Mr Pelham; Mr Annesley and the protocol for petitioning for a peerage in Ireland; question in the Houses about Hanoverians not continuing in the pay of Great Britain; the Corporation of Derby; communications with the King; slow business in Ireland; travel preparations for the 3rd Duke's convoy; the trial of a peer [Lord Santry]; a bill against burning land; reinforcement of troops in Flanders; movement of troops; augmentation of the Horse and Dragoon squadrons; death of Lord Abercorn; Captain Weller; Lord Winchelsea; draughts; the matter of deducting pay from men on ships for provisions and Mr Wade's disapproval of this idea; the bill for regulating of trials rejected; the Act for annulling of marriages celebrated by Popish priests of degraded clergymen; observations of the comet (1743); orders sent to Mr Potter; the threat from French ships; detailed account from two captains who were convoying merchants going to Jamaica with provisions; the suspension of 3rd Duke's voyage to England; accounts from the Admiralty concerning the French and British movements; French embarkation at Dunkirk under the command of Count de Sax; news from the continent including Mr Matthew's destruction of Spanish fleet; Lord Galway taking the Buxton waters - a new remedy; contradictory reports about the French King; the future of 'the Club'; a matter concerning the protection of William Jebb and discharging him for misconduct without Capt. Wickham's knowledge [reference to "Alderman Cunliffe not finding a man in his room"; account of the Jacobite rebellion; Sir William Yonge's offer to discipline the Militia [raised at Derbyshire]; his advice that the Duchess leave the countryside on account of the threat of the rebels; the assumption that the rebels will not make it to Derbyshire (CS1/294/26); preparations for defending the country from the rebels; advances of the rebels; Duke of Montagu; siege of Bergen op Zoom; French fleet seven leagues off Ushant from Brest; fleets heading to America; going to Ireland to support Lord Hartington.
In his letters to Lord Hartington, Lord Duncannon writes of: an account from Mr Boscawen of the French off Newfoundland's coast; Lord Hartington's request for some Madeira wine; a report from Bob Monkton in North America; the possibility of Lord Duncannon going to Ireland; leaving the Primate out of the Government of Ireland; Mr Ram; Lord Hartington's champagne and burgundy from Calais; serving Lord Hartington with pleasure; carrying out Lord Hartington's commands; an account of unfortunate affair of Braddocks near the Ohio and having "Indians" with them [Native Americans]; Irish beef; an account of Sir Edward Hawke; Mr Langrishe; government cabinet appointments.