Mr Cameron's advisers accept that the election will not be decided until the campaign itself, when the scale of the changes he proposes will at last be clear for all to see. But the first test will be the Norwich North by-election at the end of next month, which follows the resignation of Labour MP Ian Gibson. The Tories need an 8.3 per cent swing to win, which, on a national level, would give the party a useful majority. Failure is not an option. Mr Cameron privately expects a victory, the first wave of a flood that will sweep him and a new generation of Conservatives into power, and leave those who still do not "get" what's going on far behind.