Alan Jackson

Alan Jackson, father of Maria Jackson and ex-husband of Chrissie Jackson, was a neighbour of journalist/alien hunter Sarah Jane Smith. He was, by trade, a computer security consultant; as a result, he had considerable computer expertise as well as some unorthodox contacts.

Unlike his daughter and ex-wife, Alan was affected by the Bane in Bubble Shock!.

When his daughter was erased from history by The Trickster, only Alan could remember her--thanks to an alien device given to Maria by Sarah Jane. When he interrogated Andrea Yates about Maria's disappearance, the Graske chased him and tried to remove him. But Alan trapped the Graske and forced it to tell him where Maria went. When the day was saved, he was very surprised to find out what his daughter had really been doing with Sarah Jane Smith. (SJA: Whatever Happened to Sarah Jane?)

Alan and Maria were holidaying in Cornwall when the Earth was relocated to the Medusa Cascade and subsequently invaded by the Dalek fleet. (DW: The Stolen Earth)

In 2009, Alan was offered a new job at the head offices of his firm, in America. He accepted, and soon afterwards, he and Maria moved to Washington.
 * It's unclear whether Alan meant Washington state or Washington D.C.