Rutan scout

A Rutan scout who later came to be known as Rupert the Rutan came to Fang Rock in 1969. Due to a malfunction with its Osmic projector, the Rutan traveled back in time and split in two. One of the Rutans arrived in 1902 and was defeated by the Fourth Doctor, while the other arrived in 1822 and lived on Earth for over a century.

History
Having studied all planets in the Sol system, Earth was chosen as the best to serve the Rutan Empire's plot to destroy the Sontarans. The scout was sent to Earth for reconnaissance.

As it arrived on Fang Rock, the Rutan was caught in a paradoxical situation; Anne Travers' experiments with a version of the Rutan's osmic projector that had already travelled through time interfered with the Rutan's osmic projector and caused it to temporally malfunction and travel back in time. In a process similar to binary fission, the malfunction caused the Rutan to split into two identical Rutans which were both sent to different years. (PROSE: Beast of Fang Rock)

Rutan sent to 1902
One of the Rutans arrived in 1902, although it's pod was damaged along the way. Unaware that it had travelled through time, the Rutan followed standard procedure for a damaged ship and set out to establish a base with a power source and to create a beacon to bring the Rutan Battlefleet to Fang Rock. (PROSE: Beast of Fang Rock)

There it established the beacon and began to kill the lighthouse keepers and shipwreck survivors, one by one. Using recent Rutan technological developments, the Scout shape-shifted into the form of the lighthouse keeper Reuben Whormby. It electrocuted the others.

After a short talk with the Fourth Doctor, the Rutan attempted to take the lighthouse. Leela destroyed it with a makeshift mortar and gloated over the scout as it lay dying. (TV: Horror of Fang Rock)

Three regenerations later, the Doctor was forgiven by the Rutan Host for killing the scout. (PROSE: Shakedown)