Journalist Camilla Cavendish is leaving the Sunday Times to head up the Downing Street policy unit.
The Sunday Times associate editor and columnist, a contemporary of the Prime Minister's at Oxford University, wrote recently that an opt out from freedom of movement "must be a red line" in negotiations over the UK's relationship with the European Union.
The move follows follows news on Monday that Daily Mail political editor James Chapman is joining Chancellor George Osborne as his director of communications.
Cavendish won the Paul Foot Award in 2008 for her campaigning journalism highlighting injustices in the family court system.
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