I can trace back to a sailor who inherited a distant relative’s estate on the Isle of Bute in Scotland in the 1700s. He then married a woman from a reasonably well-off Scottish family that was from an illegitimate branch of the Campbells of Cawdor. That family produced prominent estate and plantation owners on Tobago. They married into the Campbells of Airds. This taken together, I can follow noble pedigrees back to the earliest kings of Scotland and Dal Riada, if those earliest pedigrees aren’t made up. I have other lines that can back as far, but this one is the only one I’m 100% sure about because I have the church records, saisine records, court case decisions, etc. to back it up.
The more interesting question is the most recent ancestor of significant note that I have. It’s either
Sir Duncan Campbell, 1st Baronet of Glenorchy
https://en.wikipedia.org/wiki/Duncan_Campbell_of_Glenorchy
Colin Campbell, 6th Earl of Argyll
https://en.wikipedia.org/wiki/Colin_Campbell,_6th_Earl_of_Argyll
Or
Hector MacLean, 15th Chief of Clan MacLean
https://en.m.wikipedia.org/wiki/Sir_Hector_Og_Maclean,_15th_Chief