[Cawing] Narrator: Caesar announces he'll leave for Parthia in 3 months' time, shortly after the middle of March, known to the Romans as the Ides.

Wallace-Hadrill: He's always happiest at the head of an army, defeating visible foes.

The toughest foe of all is the foe you can't see, is your old friends and your old enemies plotting together and sinking a knife in your back.

Narrator: Before he leaves for Parthia, Caesar uses supporters in the Senate to create him a role that will consolidate his power indefinitely.

Holland: They offer to make him dictator not just for 10 years, but perpetuus, forever.

Which means that if he accepts, no one will ever be able to take his dictatorship away.

♪ Wallace-Hadrill: It's a quite extraordinary thing.

A really, really explicit contravention of Roman customary practice.

The entire idea of the non-monarchical state is that no one has power in perpetuity.

♪ Holland: There is a moment when Caesar dooms himself.

It's when he accepts the office of dictator in perpetuity, dictator for life.

Because up until that moment, it had been possible for other senators to envisage a time when the normal rhythms of the Republic would be restored to them.

♪ Tempest: Step by step, Caesar is being corrupted by this power he's got.

The moment he accepts the title dictator for life, the mask comes off.

He is not going to restore the Republic.

The Roman Republic, as the Romans have known it for so long, is on the brink of collapse.

♪ Chakrabarti: Cassius saw this coming.

He said, "I told you so "when he wanted to appoint the magistrates.

"I told you so when he wanted to be "a dictator for 6 months, let alone 10 years, "and now in perpetuity.

I saw this coming."