Take context from the input text and decide on the accurate relationship between 'Russell Group' and 'London' from the options provided.
Options: legal form, owned by, owner of, headquarters location

* Rolls-Royce's biggest shareholder ValueAct is in for the long haul Elsewhere, the London Stock Exchange Group began to reap the benefits of acquiring the Russell Group , as robust growth in the index business helped Europe’s oldest independent bourse post a 27pc rise in half-year adjusted operating profit to £366.1m.
headquarters location