Doctor Who: 7 Times The Doctor Was Betrayed By Their Companions

Distraught at the sudden death of her boyfriend Danny Pink, Clara's grief caused her to act in a rash manner, betraying the Twelfth Doctor's trust by threatening him with the destruction of his TARDIS keys - every single one of them.

From Clara's point of view, this was an attempt to bribe the Doctor: she wanted him to save Danny, to change the timeline so that he doesn't die. Unfortunately though - and as we viewers very well know - the Doctor doesn't respond too heartily to the prospect of altering a fixed event, and so, he refuses her not-so-kind offer.

In response, Clara throws all seven keys into a nearby volcano, completing her betrayal by following through with her threat. For one shocking moment, it looks like the Doctor will be locked out of the TARDIS forever.

But obviously, the show must go on - in every sense of the phrase. And so, a cool twist reveals that the Doctor had been in control the entire time, having planted a dream patch on Clara's palm in an earlier scene. This meant that the whole key-destroying affair had been nothing more than a vision.

Technically then, Clara didn't cause any real damage. But regardless of this fact, she fully intended to betray the Doctor, because, unlike him, she didn't know that she was dreaming.

The conclusion of this sequence then leads to one of Twelve and Clara's most memorable exchanges: deciding to forgive her, the Doctor states "Do you think I care for you so little that betraying me would make a difference?"

The Doctor may be a little cold sometimes (especially grumpier incarnations, like Twelve) but the character truly does have a heart of gold.