Vladimir Putin has ruled Russia with three things: money, propaganda and terror.

When the Russian economy was booming and the oil price was over $100 a barrel, Putin ruled Russia almost entirely with money – throwing cash at the elites and at the people – with a small dose of propaganda and a tiny injection here and there of terror.

Now the money is running out, the equation has shifted.

Today, Russia is ruled mostly through propaganda and terror.

Boris Nemtsov took not a step nor a breath that wasn't under the intense surveillance of the FSB.

Just like all opposition leaders in Russia.

Boris Nemtsov. Reuters Nothing Boris Nemtsov did was not bugged, tailed, filmed or monitored by the secret police.

It is quite simply impossible that this man could have been shot dead without the Kremlin knowing there was a plot afoot to kill him.

This means the murder of Boris Nemtsov was either ordered or allowed to happen: which come to exactly the same thing.

That he could be killed like this has shaken the oligarchs and the officers of the Russian elite to their core.

Boris Nemtsov was once Russia’s deputy prime minister and a protégé of Boris Yeltsin.

He was almost picked as a successor instead of Putin. His murder means that the Putin’s solemn – and public – promise not to touch Yeltsin and his allies has been torn up.

This means the old Moscow rulebook has been torn up, too. Ever since fall of Khrushchev power in Moscow has changed hands without executions. Once ousted, old ruling cliques were allowed to live their lives out in irrelevance. Ripping this up works perfectly for Putin.

Those contemplating, even in the abstract, a coup know they could be executed for it – and those loyal to Putin now believe that they must fight to keep him in power as they could be executed in revenge should he fall. Vladimir Putin now has the elite exactly where he wants them: terrified.

Ben Judah is the author of Fragile Empire: How Russia Fell in and Out of Love with Vladimir Putin.