By Allegra Stratton
Political editor, BBC Newsnight
No-one would be more depressed than Steve Hilton that I'm on a train back from seeing family to talk about the departure for academia and Stanford University of the PM's closest adviser and one time backpacking pal tonight.
He's a work-life balance aficionado, if not zealot (difficult to work inside Downing Street and really bail the office that early in the day).
But any man who makes his own Ottolenghi pastry is able to appreciate the ideal of carving out a little free time (yes he does knead pastry).
Actually I don't mind heading back. Hilton is one of public life's fascinating characters.
My sources say this is not goodbye, au revoir or whatever is Californian for ciao... but actually a precursor to a more public life for Hilton.
Those who know him best say he'll be back next September because he and his wife intend to educate their kids in the UK and their older son will start school then.
With that timetable, Hilton and Rachel Whetstone decided to get in another year abroad before that became too tricky.
But when he's back, it might not be to the room he used to have outside the PM's in Downing Street for too long.
Friends say he's maybe out of love with being an adviser (your policy ideas get mangled and a spoof Twitter account is more famous than you).
He might try to set up another business - he's the driver behind the PM's moral capitalism riff - but his long-held desire to become a mayor for the town where he grew up, Brighton, is a nearer possibility than a receding one.
For the next year he will continue to work on projects for Cameron from Stanford. And British public life has a stronger, not weaker, pull.