Utilize the input text as a context reference, choose the right relationship between Free Tibet and London from the options. Options: product/material produced, manufacturer, distributed by, industry, position held, original broadcaster, owned by, founded by, distribution format, headquarters location, stock exchange, currency, parent organization, chief executive officer, director/manager, owner of, operator, member of, employer, chairperson, platform, subsidiary, legal form, publisher, developer, brand, business division, location of formation, creator.

Groups including Amnesty International and Free Tibet are planning protests throughout the state visit, starting with one during the carriage procession through central London on Tuesday.

Answer: headquarters_location