April 6th Two big dates in Pink Floyd History: In 1968 Pink Floyd announced founder Syd Barrett had officially left the group. Barrett was suffering from psychiatric disorders compounded by drug use.
In 1987, Roger Waters' lawyers issued a statement that Roger believed himself to be the creative driving force behind Pink Floyd and therefore he would contest the use of the name by anyone else and any former members of Pink Floyd.
The story does have a happy-ish ending, Roger apologized. Here is a link to the Rolling Stone article: https://www.rollingstone.com/music/news/roger-waters-regrets-pink-floyd-legal-battle-20130919