Others argued that Mantel's real target was not Kate but the press. On the Daily Telegraph website, journalist Catherine Scott said Mantel's speech was "an attack on how some parts of the media canonize royal women ... while also rendering them voiceless and purposeless."
The royal couple's office declined to comment, while a call placed with Mantel's agent after business hours went unanswered.
Meanwhile, large numbers of journalists and photographers were on hand Tuesday to watch the duchess as she visited a center for recovering addicts. It was one of her first public appearances since announcing in December that she was pregnant. News reports commented on the duchess's baby bump, gestures, demeanor and Max Mara dress.
Mantel won the prestigious Booker Prize in 2009 for "Wolf Hall" and in 2012 for "Bring Up the Bodies," novels set at the court of King Henry VIII and centered on the king's search for a queen who will give him a male heir.
Her speech touched on royal figures from Henry's wife Anne Boleyn to Kate.
Mantel said Diana "passed through trials, through ordeals at the world's hands." She said Diana's younger son, the 28-year-old Prince Harry, "doesn't know which he is, a person or a prince" — a confusion Harry himself recently remarked on.
And Kate, whose first child is due in July, finds herself cast by the press as someone whose "only point and purpose (is) to give birth," the author said.
Of the U.K.'s royal family, Mantel said: "However airy the enclosure they inhabit, it's still a cage."
Mantel ended her speech — ironically, given the media furor now — with a plea for us all "to back off and not be brutes."
London Review of Books: www.lrb.co.uk
Jill Lawless can be reached at http://Twitter.com/JillLawless