Analyze the relationship between 'Premier Oil' and 'LONDON' within the context of the input sentence.
Options: stock exchange, headquarters location, creator, distribution format

LONDON (ShareCast) - Premier Oil (LSE: PMO.L - news ) rallied after Jefferies upgraded the stock to 'buy' from 'hold' and raised the price target to 185p from 170p, on the basis of "continued operational delivery in 2H15".
headquarters location