I spotted that article too - a good read.
Francis DYMOKE is Head of that LG family of Scrivelsby, and his father, John, is treated in Burke's Landed Gentry 1952 as Head of the family (within the lifetime of Francis' grandfather Lionel), showing the lineage from Norman times and recording their roles at the coronations. The MARMION family were originally granted the Scrivelsby estate, and it passed into the DYMOKE family by marriage in the late 14th century. As the Telegraph records, the right to act as Champion is tied to the land, rather than the bloodline.
Of interest BLG 1952 also records an unsuccessful attempt of the family in 1814 to claim the Baron MARMION title, an old barony by writ long in abeyance.