Conservative Party headquarters is preparing a detailed "attack dossier" in preparation for Mr Corbyn winning the Labour leadership. Researchers have been tasked with digging through voting record and public comments of the leadership front-runner going back over more than two decades. The material will then be fed into policy advisers preparing David Cameron and other ministers for questions in Parliament.
Publicly, senior Conservatives have avoided making political capital out of Labour's increasingly fractious leadership race. But privately, the Tories’ high command finds it hard to conceal its delight over likely victory of Mr Corbyn. The Tories intend to define his views against those of other senior Labour figures in an attempt to highlight the all too real divisions within the party that will come under intense scrutiny should he win.
They intend to define him early on in the wider public mind as a dangerous ideological zealot - highlighting his opposition to Britain's nuclear deterrent his support for Hezbollah and past relationship with the IRA.
They will also claim that his victory means Labour has been captured by the hard left inspired by the new Syriza-led Government in Greece -with similar results should he gain power.
A Tory source said: "We are certainly not sitting by to wait and see what happens. We may not be saying anything publicly but it would be fair to assume that we're working on what a Corbyn victory means for us and how to respond to it.Come September we will be ready."