The doors of Rome's Sistine Chapel officially lock tomorrow morning as the conclave selects a new pope. 

135 cardinals from around the world will vote on a successor to Pope Francis, who was laid to rest almost two weeks ago. 

There's no timescale for how long it'll take, but the last two papal elections lasted for two days. 

Europe Correspondent Gavin Grey told Ryan Bridge it's set to be most secretive election of all time.  

He says there'll be no televisions, newspapers, or radio, and they can't even open the windows. 

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