Lobus Caecilius
Lobus Caecilius was a man who lived in Pompeii before Vesuvius erupted in 79. Husband of Metella and father to Evelina and Quintus, Caecilius was a marble trader with political ambitions; it was to impress Lucius Petrus Dextrus, high priest of the Cult of Vulcan, that he bought the Tenth Doctor's TARDIS at the market, intending to display it as "modern art".
Along with his family, Caecilius was spared from the devastation of Pompeii by the timely intervention of the Doctor. By early 80, Caecilius and his family had resettled in Rome, and adopted the Tenth Doctor and Donna as their household gods. (TV: The Fires of Pompeii)
Behind the scenes
The name game
This character's surname was — by Russell T Davies' admission in The Italian Job — derived from books in the Cambridge Latin Course, elementary Latin books about real, historical people. For this reason, it is frequently asserted that this character is meant to be a "celebrity historical character" in the vein of Charles Dickens or Agatha Christie. Many people, including at least one official merchandise licensee, believe that this character is Lucius Caecilius Iucundus.
Though both plausible and beguiling, it's simply not the case.
In the first and most important place, the script actually names him Lobus Caecilius upon his introduction to the Tenth Doctor; the words "Lucius" or "Iucundus" are never used in connection with Capaldi's character.
Secondly, the official website contains video which gives the character the first name of "Lobus" in its poster frame.
Finally, careful attention to RTD's words in The Italian Job reveal that the show runner merely nicked the family name from Cambridge Latin Course books. It the authorial intent that this character be a genuine historical figure. Instead, Davies characterised the use of the name "Caecilius" as a gag, supporting the many other broad Latin gags in the episode that were reminiscent of Davies' beloved Asterix' comics.
The Capaldi jobs
Actor Peter Capaldi later played John Frobisher in Torchwood: Children of Earth. Russell T Davies, interviewed for Torchwood Declassified, suggested that Frobisher may be a distant descendant of Caecilius.
The two roles have exactly opposite paths, in at least one sense. Lobus' family entirely survives due to the Doctor's largesse, while Frobisher's family entirely dies by Frobisher's own hand.
