On page 130 of The last days of Richard III and the fate of his DNA, John Ashdown-Hill described John Talbot of Lacock, father of one of the many Barbaras in Richard’s mtDNA, as “John Talbot belonged to a cadet line of the descendants of the great John Talbot”, but there is no table to illustrate this precise point. This Ashdown-Hill article, however, includes the full line on page 12.
We can now observe:
1) That Barbara, later Viscountess Longueville, is indeed descended from the first Earl of Shrewsbury, “Old Talbot”, whose daughter Lady Eleanor was Richard’s sister-in-law.
2) Sir Gilbert Talbot II, whose father was among Barbara’s ancestors, married Anne Paston, who ought to share Lady Eleanor’s mtDNA and had three daughters by her.
3) Barbara’s great-great-great-nephew was William Henry Fox Talbot, the photography pioneer.
Sir Gilbert I, grandson of “Old Talbot” was the progenitor of an interesting cadet line. The portrait is from John’s website