Graham Hook moved to Interel after the 2010 general election, having been an assistant director in the Conservative Party's research department.
At Conservative HQ, Hook managed the ‘briefing team’, responsible for briefing David Cameron and members of the shadow cabinet for high-profile media appearances.
It is understood he will primarily advise Greening on policy. He is expected to take up the post immediately.
The Transport Secretary has hired Victoria Crawford, a senior Conservative Party press officer, as her second special adviser. Crawford will be responsible for handling the media.