LONDON (Reuters) – Britain could block Russian companies from raising capital in London and expose property and company ownership in London and elsewhere if Russia invades Ukraine, Prime Minister Boris Johnson said on Tuesday. Britain, the United States, the European Union and other allies have warned they would impose heavy economic sanctions on Russia the moment any invasion occurred. Russia says it has no plans to invade and that some military units were returning to their bases. Last week Britain put in place new legislation enabling it to impose broader sanctions than it previously could …