The Robert Koch Institute has indicated that the UK is no longer a risk area:
https://www.rki.de/DE/Content/InfAZ/...ublicationFile
What does this mean for travel from the UK? In my case I have business reasons to enter Germany and it seems that I can travel to Germany from 18th April without having to quarantine, although I still need a 48-hour PCR test. I would expect that I would also only need an invitiation letter from my business partner to enable entry to Germany. Is this too simplistic an assumption?