Boswell met the Earl in the evening of August 24, 1773, as he and Dr Johnson visited Slains Castle, the seat of the Earl, north of Aberdeen. They had spent most of the day there on an invitation from Charles Boyd, the Earl's younger brother, and were invited to stay the night. The Earl arrived home around nine in the evening, together with a Captain Gordon of Park1, and they had a late supper. 

Boswell later wrote that he was "was excessively pleased with Lord Erroll. His stately person and agreeable countenance, with the most unaffected affability, gave me high satisfaction," adding that "I could with the most perfect honesty expatiate on Lord Erroll’s good qualities as if I was bribed to do it. His agreeable look and softness of address relieved that awe which his majestic person and the idea of his being Lord High Constable of Scotland would have inspired."