Chain principle

Rule 9 of the UK Takeover Code obliges anyone who acquires interests in shares carrying 30% or more of the voting rights in a Code company to make a cash offer for the whole of it. The chain principle extends that obligation one link upstream: acquiring control of a company which itself holds 30% or more of a Code company can trigger a mandatory offer for the downstream company as well.

The reason it exists is straightforward. Without it, control of a listed company could always be bought indirectly, by acquiring whatever entity happens to hold the stake, and the protection Rule 9 gives to minority shareholders would be trivially avoidable.

It is not automatic, and this is the part candidates get wrong. The Panel considers whether securing control of the downstream company was a significant purpose of the acquisition, or whether that holding is significant relative to the company actually being bought. A small legacy stake inside a large industrial group will usually not trigger it. A holding company whose main asset is the listed stake almost certainly will.

The practical lesson is about process rather than doctrine. The trigger sits inside a transaction that may have nothing to do with the listed company, so it is found by consulting the Panel early, not by a careful reading of the rule in isolation. The Panel gives rulings in real time, which is one of the ways the UK regime differs from regimes that resolve these questions through litigation after the event.