Isambard Kingdom Brunel

Isambard Kingdom Brunel was an engineer and — in the words of the Eighth Doctor — "the man who built the modern world".

Brunel designed the Clifton Suspension Bridge, the SS Great Britain, the Thames Tunnel, the Tamar Bridge and Paddington station. He also made significant contributions to the Great Western Railway.

At some point, one of the first five incarnations of the Doctor met Brunel and acquired his business card, which he kept in his address book. (TV: The Two Doctors)

The Sixth Doctor met him in 1828 in one of his father's tunnel. He helped the Doctor investigate something strange in the tunnels and came through a strange city under the river. He came with him and encountered Rispa. He stole the TARDIS key and wanted to pilot the TARDIS away. (AUDIO: Iron Bright)

In Juliet Kemp's home, the ghost of Isambard Kingdom Brunel was trapped inside a tea cosy. (PROSE: Contributors)

Alternate timeline
In an alternate 1843, the Eighth Doctor, Fitz Kreiner and Anji Kapoor met Brunel in a timeline created when the mysterious Eternines attempted to alter history, draining energy from Earth to sustain their own world. As a result of these changes, their agent, Jared Malahyde, offered Brunel some vital assistance in constructing his major projects in 1831, resulting in Brunel completing such projects as the Clifton Suspension Bridge earlier than in the original course of events. After meeting the Eighth Doctor and being saved from the Cleansing, Brunel was taken into the future that would result from these events. He sacrificed himself to give the Doctor to chance to undo this new history, erasing all memory of his encounter with the Doctor. (PROSE: Reckless Engineering)