What is the relationship between Worldpay and London in the context of the input sentence. Choose an answer from: 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.

** British payments processor Worldpay Group listed on the London Stock Exchange on Tuesday in an initial public offering valuing the company at 4.8 billion pounds ($7.4 billion), the biggest flotation in London this year.

Answer: headquarters_location