Professor Eustacius Jericho was a parapsychologist who lived in the village of Medderton. He was an academic who sought a breakthrough in his field, though always lost out to "better men". In November, 1967, he examined the mind of Claire Brown, a percipient whose mind was the refuge of a Weeping Angel. As a result, he was displaced in time to 1901.
By 1967, he was living in a house on the edge of the village of Medderton, overlooking the sea. He owned bees, though had neither a partner, nor any children. He was conducting experiments in the field of parapsychology. Jericho had taken on Claire Brown, a percipient who had experienced a series of premonitions, as a patient and subject for his examinations.
On 21 November, he was conducting a lie detector test on Claire when he encountered the Thirteenth Doctor and the Weeping Angels. He managed to stall the Angels until he blinked and was sent back to 1901, where he met Yasmin Khan and Dan Lewis. (TV: Village of the Angels)
Over the subsequent three years, Jericho travelled across the world with Yaz and Dan in search of information regarding the Flux. After a chance meeting with Joseph Williamson, their travels eventually brought them back to England (TV: Survivors of the Flux) in 1905. (TV: Eve of the Daleks) Upon arriving in Liverpool, the three explored the Williamson Tunnels where they encountered Williamson once again. Williamson showed them the purpose of the tunnels: to allow him to guard doorways to multiple different points in time and space. Jericho and the others later fell victim to a Sontaran attack. (TV: Survivors of the Flux)
The group retreated through the tunnels, travelling to 5 December, 2021. Here, he reunited with the Doctor and accompanied her back to 1967 to recruit Claire into the Sontaran resistance. Jericho and Claire were selected by the Doctor to act as spies within a Sontaran ship, as the Sontarans' Psychic Command required a human psychic to send a message to their foes, the Daleks and Cybermen. Eventually, Claire managed to escape, unintentionally leaving Jericho behind.
After a time, the Battalion wall moved, outnumbering the fleets, including the one Jericho was on, where he was facing certain death from either a Sontaran or the Flux. Although the Doctor contacted Jericho and advised him to get into an escape pod, Jericho chose instead to face his death with dignity. As the Flux broke through the ship, Jericho's last words were "What an awfully big adventure." (TV: The Vanquishers)
The Thirteenth Doctor considered Jericho to be a "proper scientist": when his house came under seige from the Weeping Angels, Jericho didn't stop to be scared, but just wanted to understand what was beyond his comprehension. The Angels saw him as a loveless, childless professor, hiding in academia for fear of the real world. He was so interested in other minds because he couldn't bear to examine his own. He sought a breakthrough in the field of parapsychology, though deep down considered himself a failure as he was "always losing to a better man".
Jericho felt duty bound to help those around him. He was a soldier in the British Army, where he helped to liberate Belsen. After being displaced by a Weeping Angel to 1901, he thought not of himself, but of the Doctor who he had left "in the most terrible trouble". (TV: Village of the Angels)