She’s his great-great-great-great-great-great-great grand mummy.
The mysterious mummified corpse of a woman with syphilis who died in Switzerland centuries ago has been revealed to be a direct ancestor of British Foreign Secretary Boris Johnson.
Her body was discovered during renovations at the Barfüsser Church in Basel in 1975, preserved in part by the large amount of mercury believed to have been a treatment for syphilis.
It has been believed that the mummy was part of the wealthy Bischoff family in Basel, and new DNA tests reported Thursday by the BBC and Switzerland’s SRF show that body belonged to Anna Catharina Bischoff.
The descendants of Bischoff, who lived from 1719 to 1787, who trace their through generations of families called von Pfeffel and Williams, include Yvonne Williams, who married Johnson’s grandfather Wilfred Johnson Kemal.
Johnson has not publicly commented on the new certainty about his heritage, and it is unclear if his DNA was used to discover matches with that found on the mummy’s big toe.
Boris Johnson serves as Foreign Secretary under British Prime Minister Theresa May.
The exact circumstances of Anna Catharina Bischoff’s life are also unclear, though the BBC reports that she appears to have contracted syphilis while working to cure patients with the disease in France.
The Foreign Secretary has previously spoken about his ancestors as “posh toffs” after learning about their upper class origins.
Wilfred Johnson did not know his father Ali Kemal, though the latter was a Turkish politician and opposition journalist murdered in the 1920s.
Closer relatives of the current British diplomat, whose career highlights include ziplining though London as mayor and speculation about a prime ministership after his support for Brexit, continue their ancestors’ aristocratic traditions.
Johnson’s father Stanley Johnson was a member of European Parliament and World Bank employee, while his brother Jo Johnson is a member of British Parliament and his sister Rachel Johnson is a prominent journalist.