MSS.7003-7022, Letters to the 1st and 2nd Marquesses of Tweeddale, with a few letters concerning them, 1661-1713, forms a separate sequence but because of the way some of the manuscripts have been bound this distinction could not be represented exactly in the hierarchy of the descriptions.
Of the letters written before 1697 (the year of his death), by far the greater number are addressed to the 1st Marquess; but occasionally it is not certain whether the addressee is the 1st Marquess or his son.
Of the letters to the 1st Marquess, those most directly concerned with public affairs are dated 1661-1674 and 1690-1697, since he was out of office for much of the intervening period. The chief correspondents on public affairs in the earlier period (apart from the Duke of Lauderdale, most of whose letters are collected in MS.7023) are Sir Robert Moray and the 2nd Earl of Kincardine; and in the later period, Sir Alexander Bruce (later 4th Earl of Kincardine), Sir Archibald Murray, Sir James Steuart, Colonel John Hill (writing about the massacre of Glencoe), and the successive Secretaries of State for Scotland. For official correspondence of the Privy Council, the Commissioners of the Treasury, and other bodies of which the Marquess was a member, see MSS.7032-7035.
As well as the letters on public affairs there are many letters about the family estates and legal affairs, in particular the protracted lawsuits with the Duchess of Buccleuch (niece of the 1st Marquess's wife), and with the Duke of Lauderdale (father-in-law of the 2nd Marquess). The chief correspondents here are Sir Patrick Murray, Lord Newbyth, and Andrew Hay. There are also many letters from members of the family including some written on the Grand Tour by the 1st Marquess's brother, William, by his sons, David and Alexander, and by his grandsons, John and William; some letters describing the Flanders campaigns of 1692-1694 from his grandsons, John and William; and a long series of letters from his daughter Margaret, Countess of Roxburghe.
Most of the letters written to the 2nd Marquess after 1697 are on public affairs. They include letters about the Darien Scheme, 1698-1701, and a series of letters from Lord Yester (later 3rd Marquess) describing the political events in London, 1708-1710.