One for the magnificent dressers. Thames goes wonderfully off-script for four days of steampunk madness, with markets, competitions, dancing, high tea, a Victorian ball and some seriously committed costuming. It's family friendly too, so bring the kids, polish the goggles, fluff the bustle and embrace the theatricality. Even if steampunk isn't normally your thing, the people-watching alone is glorious — and so is the street parade.