Question: What post-WWII British spectacle opened to the public on May 4th, 1951?
Answer: The Festival of Britain, which showcased British industry and arts so as to promote the vision of a better Britain after all the upheaval of the war years. Perhaps something similar will come into being after the world’s current crisis is over.
https://www.historic-uk.com/HistoryUK/HistoryofBritain/The-Festival-of-Britain-1951/