Circular Time (audio anthology)

 was the ninety-first release in Big Finish's monthly range. The four stories were writen by Mike Maddox and Paul Cornell respectively and featured Peter Davison as the Fifth Doctor and Sarah Sutton as Nyssa.

Released in 2007, it was the company's first attempt at an audio anthology in the Main Range. Its critical and popular success paved the way for the release's then-unique format to be repeated annually.

The theme of the compilation, as suggested by the title, was the passage of time — specifically the time of the friendship between Nyssa and the Fifth Doctor. A story was taken from each of the major periods of their friendship's life — spring, summer, autumn and winter — to indicate how it matured. Each story was also of a different genre — adventure with aliens on a distant planet, celebrity historical, character piece, and high-concept adventure. Despite the presence of a cohesive theme, however, the stories shared no narrative continuity at all.

Publisher's summary
Summer to winter, the seasons turn. In the springtime of a distant future, the Doctor and Nyssa become embroiled in Time Lord politics on an alien world. During the stifling heat of a summer past they suffer the vengeful wrath of Isaac Newton. In the recent past, Nyssa spends a romantic golden autumn in an English village while the Doctor plays cricket. And finally, many years after their travels together have ended, the two friends meet again in the strangest of circumstances. Four seasons. Four stories. Now close the door behind you, you're letting the cold in...