Ice Warrior invasion of Earth (The Seeds of Death)

An Ice Warrior invasion of Earth based on subverting T-Mat technology was led by Slaar in the 21st century. (TV: The Seeds of Death, PROSE: The Seeds of Death)

Dating
One history book, citing Bernice Summerfield's Down Among the Dead Men, claimed that this invasion took place in the winter of 2044. (PROSE: A History of the Universe)

Other information
A Clara Oswald splinter resembling Gia Kelly was present to help the Doctor. (PROSE: Second Session)