When an overseas company wishes to establish a branch in the UK they may appoint a senior employee of the overseas branch to come to the UK, set up the UK branch, and work at running the UK branch.
Such an employee may apply for a Representative of an Overseas Business visa and if the visa is granted they may come to the UK for that purpose.
After five continuous years on that visa, the migrant may be able to apply for indefinite leave to remain.
There is an English language requirement for Representative of an Overseas Business visa applicants.