Utilize the input text as a context reference, choose the right relationship between Santander UK 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.

The communications chief at Royal Mail is heading to Santander UK in a move that will intensify speculation that the Spanish-owned bank is close to a London flotation.

Answer: headquarters_location