Ann: Change in Substantial Holding, page-11

Hi aposteriori

A substantial holder can own 19.9% of a Co and then add [from memory] 1% every 6 months without triggering the requirements to declare any intentions of a takeover.
There are no requirements that a person needs to own a particular level of shares prior to making a takeover offer. The 20% rule is to stop people from acquiring a takeover target in a manner in which the market is not fully informed ...i.e. that the shares trade at a fair market value.