O n the wide streets around Leeds’ Roundhay Park, Labour canvassers have built up a considerable step count just to walk between each of the stone-built mansions in one of the city’s most affluent suburbs. Lucy Powell, Labour’s deputy leader, is with activists in the sunshine admiring the manicured lawns and window-box pansies. This is one of the safest wards for Labour in Leeds , with graduates, doctors, lecturers and small business owners. In years gone by, voters in these houses with sweeping driveways and climbing roses would have been natural Conservatives . A short walk away is Roundhay school, the alma mater of Liz Truss, a place she amusingly tried to paint as the wrong side of the tracks. But now Labour councillors in the ward have a different adversary – the Green party . It is in these wealthy areas, as well as the more diverse suburbs and student population, that the Greens are making gains.…