What is the relationship between Deloitte 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.

The amount of office space being built in central London rose by 24 per cent in the six months to the end of March, a survey of construction activity by advisory firm Deloitte found earlier this year — the second-biggest increase in 20 years.

Answer: headquarters_location