1981 Ashes series

The 1981 Ashes series was a cricket match at which the Fifth Doctor was doubly present at two points in his life — once with Tegan and Turlough and later-but-simultaneously with Peri and Erimem. It was a contest that most versions of history agreed ended with England defeating Australia after a climactic final catch by Graham Dilley. (PROSE: Graham Dilley Saves the World)

Main version of the event
According to a newspaper report in the National Clarion filed by Digger Wells, England's win in the 1981 Ashes was simply "the greatest comeback the sport had ever seen". By the third day of the three tests, things were not looking particularly bright for England. Bookies were giving plausibly long, 500-1 odds on the side. They'd lost the first of three tests, their captain had been fired, and they were 200 runs behind Australia. The lads from down under seemed poised for all-but-certain victory. On the fourth day, though, Ian Botham stopped England's haemorrhaging with what Digger Wells called a "belligerent" 145 not out. In the fifth day, England completed its "rise from the grave" for the win. (PROSE: Graham Dilley Saves the World)

Tegan's changed history
An alternate timeline was once created by Tegan, who, while watching the fifth day of the third test of match, caused Dilley to drop an easy catch that would have retained the Ashes for England. This failure then led to a series of riots that culminated in the assassination of Queen Elizabeth II and other heads of state, massively interrupting the "natural" course of the timeline. The Fifth Doctor discovered Tegan's role in the creation of the alternate timeline whilst travelling with his later companions, Peri and Erimem, who agreed to help the Doctor stop Tegan from disturbing Dilley's catch.

Peri and Erimem were able to avert Tegan's history-changing distraction, such that the Australian was actually responsible for Dilley making the catch, and thereby restoring the "proper" version of the contest. This meant, of course, that Tegan had helped England defeat her home team, and so the immediate aftermath of the 1981 Ashes for Tegan was that Peri and Erimem took her out to drown her sorrows in alcohol. All three women therefore returned to their respective versions of the Doctor quite drunk. (PROSE: Graham Dilley Saves the World)