10 Reasons Why The New Doctor May Actually Be River Song

This leads us on to a large tell of River Song's - her use of weaponry and violence. As the Thirteenth Doctor states, the Doctor does not use guns. While Martin's Doctor did not use the gun, she certainly knew how to handle one and was not phased by its presence.

Likewise, when cornered in the chapel, Martin's character removed the horn of the Judoon Captain. While it is knowledge that both the Doctor and River Song know Venusian Martial Arts, the ruthless nature of removing the Judoon's horn is an act of violence and defiance, an act only witnessed in River's character.

We know that River has been married on multiple occasions as she tells us she learnt Venusian Martial Arts at the Venusian Martial Arts Academy during her honeymoon, after accidentally misreading a brochure. And as Ruth Clayton states "I'm married", we may assume that this is a nod to River's unknown lovers.

In River's timeline, she has not married the Doctor yet. However, she has been married and learnt the skill before their matrimony. It is not too far removed to suggest that Ruth may have learnt this specific form of Martial Arts on honeymoon, too.