To borrow a line from the Seventh Doctor, every great decision creates ripples, like a huge boulder dropped in a lake. The heavier the decision, the larger the waves, the more uncertain the consequences. A lot has happened to the Doctor in their thousands of years of time and space.

Most of the time the Doctor walks away (relatively) unscathed, brushing the dust off and jumping into the TARDIS to find the next planet that needs saving, or the next evil alien monsters that need defeating. But some moments are more pivotal than others. Sometimes, there are consequences.

And occasionally, these consequences are so great that they can fundamentally change Doctor Who as a show, sending out ripples that are still being felt years – or even decades – later. From the origins of the Last Great Time War to accidentallychanging reality with the flick of a salt shaker, these are the moments we can pinpoint as having the biggest effects on the history of the Whoniverse. 10.

Dalek Caan’s Temporal Shift Evolution of the Daleksends with a standoff between the Doctor and Dalek Caan – the last of the TimeLords versus the last of the Daleks (at least, as far as anybody knew at that point). Tired of the endless death and destruction,the Doctor shows Caan mercy, begging the Dalek to lay down its arms and finallyend the conflict between the two species. To no great surprise, Caan refuses, and instead activates an EmergencyTemporal Shift – a last-ditch randomised time and space teleporter.