This Sunday is the Croxley car show (On Croxley green). This is a very well attended show and usually about a 700 classic cars and hot rods show up. Here is a link http://www.watfordclassics.co.uk/events.htm
Over the years I have seen some absolutely amazing cars brought by their owners to this car show, Mclaren F1, Lamborghini Cheetah, Porsche 356, Early 911's, Dethomso Pantera also a great range of restored classics Model T, Bentley blower, Ford Cortina, Mini etc. and you must not forget the hotrods. It is worth visiting for a wander around for a few hours.