The party after "the main event". After a live concert, a show, ballet, conference or wedding etc. For those who want to celebrate more, for those who haven't danced enough or for those delivering the speech, the show, the performance or simply those who are not ready to go home yet.. These people all go on to the After Party. On April 29th 2011 many neighbourhood streets in the UK will be closed as people bring out their tables and line the streets with them and decorate them and share food and drinks up and down their street to celebrate Prince William & Kate's wedding day at these spontaneous After Parties literally on the streets.