The ill-fated mountaineer George Mallory's only book was "Boswell the Biographer"?
Christoph Dietrich von KellerBorn 1699
Originally an envoy from Würtemberg, he eventually joined the service of Gotha where he held various positions including that of privy counsellor (1751-), director of excise (1757-), Head of the Geheimen Ratskollegiums (1757-1760) and First Minister of Saxe-Gotha (until November 28, 1763).1
Life with Boswell:
Boswell had a recommendation for the Baron, which he sent to him in Gotha on October 17, 1764. Keller, however, was not in the city at the time, and the two does not seem to ever actually meet.
Note 1: The Journal of his German and Swiss Travels, 1764, p. 167n3