In the same year (1765) Lord Frederick was for a few months Keeper of the Privy Seal of Scotland but resigned in July following the dismissal of the Grenville administration and was succeeded in the office by Lord Breadalbane. Lord Frederick was sworn of the privy council 29 May 1765, made Lord Clerk Register for Scotland in 1768, and confirmed in that office for life in 1777. In 1774 Lord Frederick had laid the foundation-stone for a register house at Edinburgh, and procured a permanent establishment for keeping the records, and received the thanks of the court of session. He was elected Rector of Glasgow University for 1772–73.