A source told The Sun: "The announcement is a formality. The truth is the marriage has been dead for months.
"They just never got on once the spotlight disappeared and they were left with the dull reality of their relationship.
"They just rushed into it hoping for the best and it has all gone pear-shaped. Alex is more depressed about it than she is. She was his meal ticket, and he knows it."
There was reportedly no third party involved in the split - but the fact their entire relationship had been documented by Katie's reality TV productions can't have been easy. The couple had also been desperate to have a baby (Katie already has three).
Katie had Tweeted this week to dispel previous rumours her marriage was on the rocks: "To answer my fans questions, News of the World did a accurate story Sunday about our marriage in crises (sic) ..always look on bright side xx."