Gold shortages in the 18th century, caused by the Seven Years' War and war with Revolutionary France, began to affect the supply of gold bullion reserves, giving rise to the "Restriction period". The Bank was unable to pay out gold for its notes, and so under the Bank Restriction Act 1797 began to issue lower denomination £1 and £2 notes in place of gold guineas, that were hoarded as so often was the case in time of war. Confidence in the value of banknotes was rarely affected, except during 1809–11 and 1814–15 under the extreme conditions of war.