Kate Middleton felt isolated and humiliated after Palace made constant jabs at her mother, Carole Middleton.
According toDaily Mirror's royal correspondent Vanessa Allen Carole does not enjoy a good reputation amongst royals.
"She [Carole] is pushy. Rather twee and incredibly middle class. She uses words such as ‘pleased to meet you’, ‘toilet’, and ‘pardon’," Allen said.
Another Palace insider added, "William got on well with Carole. He liked flopping down on the sofas of their Berkshire home, enjoying the normality of that.
"The Queen was fond of Kate and liked her father. But let's just say there was a feeling that Mrs Middleton was not right or acceptable."
Reports at the time added that Prince William couldn't keep "away from the fact that his future mother-in-law was looked down upon in senior royal circles."