Ann: Becoming a substantial holder, page-4

Not much. Richard Branson has decided to list Virgin Orbit and is doing so by merging with NextGen Acquistion Corp, a listed US company. As a consequence of signing the merger agreement, NextGen has acquired a legal interest in the shares in SAS held by Virgin Orbit and has to declare this to the ASX.

(NextGen is a SPAC. SPACs are listed shell companies that raise capital on the promise of merging with a real company. Effectively Virgin Orbit will be doing a reverse takeover of NextGen, much like SAS did to Burleson Energy a few years back...)