From TARDIS Index File, the free Doctor Who reference.

Lucius Caecilius Iucundus
Also known as:	Caecilius
Race:	Human
Home Planet:	Earth
Home Era:	A.D. 79
Appearances:	DW: The Fires of Pompeii
Actor:	Peter Capaldi

"The sky is falling!"

―Caecilius

Lucius Caecilius Iucundus was a man who lived in Pompeii before Vesuvius erupted in A.D. 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 Doctor's TARDIS at the market, intending to display it as "modern art".

Along with his family, Caecilius is spared from the devastation of Pompeii by the timely intervention of the Doctor. By early A.D. 80, Caecilius and his family have resettled in Rome, and have adopted the Doctor and Donna as their household gods. (DW: The Fires of Pompeii)

Behind the Scenes

• The Caecilius family (Caecilius, Metella and Quintus) were based upon characters used in Latin textbooks and the Cambridge Latin Course, which where based upon real people, but Evelina was created by James Moran so she could be a member of the Sibylline Sisterhood.
• 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. It's possible this is another instance of spatial genetic multiplicity, as referenced in Journey's End. Indeed, there was also a rift in time and space above Pompeii.