Guardian: Gordon Brown yesterday gave his strongest public hint that he will approve a third runway at Heathrow airport next month. In the face of ministerial unease, the prime minister insisted that it was right to press ahead with major infrastructure investments in the downturn. “We are making the investment in transport to ensure our infrastructure is fit for the needs of the 21st century including a decision on the third runway at Heathrow,” he said at his last monthly press …