Lloyd's of London, the world's oldest insurance market, may transfer some of its business to the European Union (EU) if the UK fails to secure single-market access after it leaves the 28-member economic bloc, according to chairman John Nelson.
Speaking on the BBC's Today programme, Nelson said: "If we do not get access to the EU single market, what will happen is that business will be written by us and others onshore in the EU.
"If we do not see a clear direction of travel, we will have to invoke our contingency plans.
"That would mean moving business, or business leaving London, more quickly than the renegotiation timetable. So therefore clarity is important."
Nelson also said around 11% of Lloyd's of London's £25bn ($33bn) in gross written premiums in 2015 came from the EU.
Post-Brexit, several insurers who work with Lloyd's of London have said they would be looking to set up regulated subsidiaries in the EU as the UK prepares to leave the bloc.