By Charles Gitonga & Andre Lombard Malawi’s government is demanding the astonishing sum of $309bn (£245bn) in unpaid taxes and royalties from a US-based gemstone company for rubies exported from the southern African state over the last 10 years, its attorney-general has told the BBC. Columbia Gem House, a family-owned business which says that it upholds fair trade practices, dismissed the claim as “baseless and defamatory”.