Detective Chief Inspector Phil Reade of Greater Manchester Police said: "This is a shocking case in which an innocent and defenceless little boy has suffered appalling injuries at the hands of someone who had been trusted to look after him.
"Rigby has today been put behind bars for a long time for his actions, but this will go little way to ease the suffering of Rio's family, who have lost their beloved little boy under such tragic circumstances."
More top news
Quickly turning cold this evening with a widespread frost developing under clear skies, some fog patches too.
The Queen says she is "deeply touched" by the "selflessness" of medical staff fighting the Ebola outbreak in her annual Christmas speech.
Video of Norman the dog's Scrooge-like disdain of Christmas is becoming a festive hit online as he moans about his owners' singing.