What is the relationship between Premier Oil 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.

445.00p +2.53% BHP Billiton (NYSE: BBL - news ) (BLT) 1,235.50p +2.45% International Consolidated Airlines Group SA (CDI) (IAG) 526.50p +2.33% Vodafone Group (NasdaqGS: VOD - news ) (VOD) 235.30p +2.28% Babcock International Group (BAB (Other OTC: BABB - news ) ) 1,098.00p +2.23% London Stock Exchange Group (LSE) 2,516.00p +2.19% Sports Direct International (Other OTC: SDIPF - news ) (SPD) 722.00p +2.19% Barratt Developments (LSE: BDEV.L - news ) (BDEV) 633.50p +2.10% Unilever (ULVR) 2,875.00p +1.99% FTSE 100 - Fallers ARM Holdings (LSE: ARM.L - news ) (ARM) 1,038.00p -0.67% Weir Group (WEIR) 1,609.00p -0.37% FTSE 250 - Risers Fidelity China Special Situations (LSE: FCSS.L - news ) (FCSS) 135.20p +4.40% Premier Oil (LSE: PMO.L - news ) (PMO) 145.30p +4.16% Zoopla Property Group (WI) (ZPLA) 238.90p +3.87% Ocado Group (Other OTC: OCDGF - news ) (OCDO) 455.90p +3.76% Vedanta Resources (Other OTC: VDNRF - news ) (VED) 471.70p +3.67% Fidelity European Values (FEV) 182.00p +3.41% Just Eat (Other OTC: JSTLF - news ) (JE.)

Answer: headquarters_location