The prime minister faced fresh embarrassment on Saturday over text messages he exchanged with former News International boss Rebekah Brooks.
In one message obtained by the Mail on Sunday, the Prime Minister thanked Brooks for letting him ride one of her horses, joking it was "fast, unpredictable and hard to control but fun".
In another the journalist, who faces trial in connection with the phone hacking scandal, praised Cameron's speech to the Tory conference, saying: "I cried twice."
The playful texts are apparently part of a cache of texts and emails handed to Lord Justice Leveson's media standards inquiry.
Very few have so far been made public - sparking accusations from Labour that they are being covered up.
Saturday's leak sheds further light on the close relationship between Cameron and Brooks, who live near each other in Oxfordshire.
Her husband, racehorse trainer Charlie Brooks, was at Eton with the PM.
Brooks told the Leveson Inquiry earlier this year that Cameron signed some of his missives to her 'LOL' - mistakenly thinking it meant 'Lots of Love' rather than 'Laugh Out Loud'.
Both of the messages disclosed by the MoS were sent in October 2009, shortly after Brooks left her job as editor of The Sun and became chief executive of News International, which owns the paper.
In one, Cameron wrote: "The horse CB (Charlie Brooks) put me on.
"Fast, unpredictable and hard to control but fun. DC."
After his conference speech, Brooks texted: "Brilliant speech. I cried twice. Will love 'working together.'"