What is the relationship between BTG 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.

194.70p -0.66% Glencore (Amsterdam: GX8.AS - news ) (GLEN) 132.65p -0.64% Marks & Spencer Group (MKS) 502.50p -0.59% Persimmon (PSN) 2,030.00p -0.59% Fresnillo (Amsterdam: FN6.AS - news ) (FRES) 598.00p -0.58% FTSE 250 - Risers Redefine International (RDI) 53.75p +2.97% Electra Private Equity (ELTA) 3,275.00p +2.34% Fidelity China Special Situations (FCSS) 117.10p +2.27% Synergy Health (Other OTC: SYHEF - news ) (SYR) 1,624.00p +2.20% DCC (Frankfurt: DCC.F - news ) (DCC (LSE: DCC.L - news ) ) 4,894.00p +2.09% Indivior (Berlin: 2IV.BE - news ) (INDV) 222.80p +1.97% Aggreko (EUREX: AGKF.EX - news ) (AGK) 1,045.00p +1.85% Derwent London (LSE: DLN.L - news ) (DLN) 3,595.00p +1.58% SEGRO (LSE: SGRO.L - news ) (SGRO) 420.40p +1.55% BTG (Other OTC: BTGYY - news ) (BTG (LSE: BTG.L - news ) ) 631.50p +1.53% FTSE 250 - Fallers Halfords Group (LSE: HFD.L - news ) (HFD) 469.80p -7.88% Diploma (DPLM) 665.50p -6.99% Premier Oil (LSE: PMO.L - news ) (PMO) 99.00p -4.53% Evraz (EVR) 68.25p -3.74% Ophir Energy (Other OTC: OPGYF - news ) (OPHR) 94.95p -3.31% Clarkson (CKN) 2,265.00p -2.37% Just Retirement Group (JRG) 187.60p -2.04% Foxtons Group (LSE: FOXT.L - news ) (FOXT) 236.10p -1.34% Debenhams (DEB) 74.00p -1.33% Tullow Oil (LSE: TLW.L - news ) (TLW) 215.80p -1.33% FTSE TechMARK - Risers Filtronic (FTC) 6.75p +8.00% Dialight (DIA (Amsterdam: DI6.AS - news ) ) 654.00p +3.32% SDL (SDL (LSE: SDL.L - news ) ) 376.00p +1.01% KCOM Group (LSE: KCOM.L - news ) (KCOM) 96.50p +0.52% Spirent Communications (Other OTC: SPMYY - news ) (SPT (Taiwan OTC: 8431.TWO - news ) ) 78.25p +0.32% Oxford Instruments (Other OTC: OXGGY - news ) (OXIG) 842.50p +0.18% Oxford Biomedica (LSE: OXB.L - news ) (OXB) 7.71p +0.13% IShares Euro Gov Bond 7-10YR UCITS ETF (IEGM) € 198.97 +0.12% FTSE TechMARK - Fallers UCW Limited (UCW) A$0.01 -6.67% XP Power Ltd (LSE: XPP.L - news ) .

Answer: headquarters_location