anchor: Both Madeira and Britain benefited from a new regulation that governed the shipment of Madeira wine and made it the only wine that could be exported directly to the British possessions in the Western hemisphere (providing, of course, it was carried by a British vessel).
positive: Britain allowed the export of Madeira wine only on the condition that it be aboard British ships.
negative: Britain stepped in and banned the export of any Madeira wine, crippling the island's economy.