Facebook Inc - is listed at Companies House (UK register of businesses) as a legal person with significant control (75%) of Facebook UK. Mark Zuckerberg is the senior officer of the significant person company that has a controlling interest in a UK company. Either an officer of the company (i,e, those listed as officers/ Directors of Facebook UK) or, as in this case, a person representing significant control(more than 50% ownership and therefore potentially a say in or responsibility for operations) of a UK company can be requested to explain a companies activities to either the UK parliament or a UK court.