Don't listen to anyone who tells you summer's over. You don't need that kind of negativity in your life. And pay no mind to your post-August bank balance, either, even if it's making you wonder if you should stay indoors all weekend batch-cooking cheap-and-nourishing lentil soup. Because although we're technically in meteorological autumn, the weather's still warm, the days are long(ish) and London's full of fun outdoor events to enjoy that are totally free.