Barton Twining (バートン・ツイニング Bāton Towainingu) was William's uncle, who took care of him after his parents death. He went missing after his business failed and went bankrupt. It's later revealed that he was behind the murder of William's parents and one of the Four Horsemen of the Apocalypse, the Pale Rider.
Barton is a well kept man, dressed as a noble, with short black hair parted in the middle. His colour scheme hasn't been fully shown yet. He has a thin mustache.
Barton appears to be a practical man, with a love of archeology. He seems to be very fond of his nephew, William. He was also the only one of his relatives that fought for young William when his parents died, the others only wanting the family fortune.
Barton had been to ruins in Ethiopia in order to look for a "treasure he wishes to obtain no matter what", his reason being that he loves ruins. He stuck up for young William after his parents' death, becoming his guardian. Sometime before the start of the manga he went to Egypt, lost all the Twining family assets, and all contact with him was lost.
He returns later to Stratford school and reveals that he was excavating ruins in the Middle East (Mount Ararat in Turkey, just when traces of the Urartu had been dug up) when he'd been caught up in some trouble and fell off his camel, losing his memory. As to how he'd lost the assets: there weren't any willing investors, so he'd thought to use his own arrears, but in reality Lord Barton's fortune was inserted into the mortgage - and he'd lost it all. 
While he had amnesia, it became troublesome with the Turkish officials so he drifted off to Poland, where people from the Christian family told him about himself. Now, he's running a successful firm and has bought back all the family assets.
- "The industry is the other God that saves the people."
Amon and Mamon • Baphomet • Eligos • Gilles de Rais • Gilgamesh • John Dee • Lamia • Leonard
Belphegor • Empusa • Lamashtu • Leviathan • Lucifel Rofocale • Pluto • Astaroth the Second • Behemoth
Adrian Swallow • Barton Twining • Bianca Clifford • Elliot Eden • Mary • William Wynn Westcott
Arthur Christian • Cassandra • Ernest Crosby • Tamar • Elizabeth Dale