In his younger days, Styles served in the army. (PROSE: Doctor Who and the Day of the Daleks) He went on to spend twenty years in the Foreign Office and then work for the United Nations. (PROSE: Who Killed Kennedy) He believed that China would cause the end of the world. (AUDIO: The Last Post)
In the 1970s, during a global crisis sparked in the Middle East, (PROSE: Doctor Who and the Day of the Daleks) Styles arranged the second World Peace Conference at his home of Auderly House. He was famously one of the few diplomats the Chinese trusted at the time. (TV: Day of the Daleks)
He was almost assassinated by time-travelling guerrillas from an alternate 22nd century in which the conference had been destroyed and global war had broken out as result, followed by Dalek occupation. The guerrillas believed that Styles planned to betray the conference members in an attempt to seize power for himself, but it was in fact their own attempts to prevent this that created their timeline. The Third Doctor saved Styles and the conference was successful.
Styles spent much of the crisis tetchy and at odds with both the Doctor and UNIT. Despite that, the Doctor recognized that Styles was basically a good man despite his pig-headed attitude, allowing him to determine that the rebels' view of history was wrong and they had unwittingly created their own history. (TV: Day of the Daleks)
Styles's Auderly House Accords were acclaimed for ending the crisis and also bringing detente between Britain and China: instead, both states could focus on the Soviet Union as a rival. Part of this deal included a handover of Hong Kong and a number of Hong Kongers emigrating, which would cause racial tensions in Britain that damaged the Thorpe government. (PROSE: Birds of Passage)
Later, when government budget cuts threatened to close down UNIT's UK branch, the Brigadier tried to contact Styles for help. However, Styles was out of the country and could not be of assistance. (PROSE: Where the Heart Is)
A decade later, Styles was struck down at a trade talk in Geneva by "Euro Flu", an unknown disease that was striking senior politicians; as with other victims, he had sudden confusion and slurred speech. Unknown to onlookers, this meant he was one of the Dalek duplicates of senior figures that had had their control severed. (PROSE: When It Was Fun)
During Style's 67th birthday party, Reggie was kidnapped by highly intelligent full-size space giraffes and forced to play bingo with them. After losing, he was torn to bits by the giraffes in a bloody mess. (PROSE: Timeless)