to this Kingdom, and to the Plantations and Colonies thereunto
belonging."

Having thus gained practically free admittance to the field, English
merchants sought to exclude other nations by securing a monopoly of the
lucrative Spanish colonial slave-trade. Their object was finally
accomplished by the signing of the Assiento in 1713.[8]

The Assiento was a treaty between England and Spain by which the latter
granted the former a monopoly of the Spanish colonial slave-trade for
thirty years, and England engaged to supply the colonies within that
time with at least 144,000 slaves, at the rate of 4,800 per year.
England was also to advance Spain 200,000 crowns, and to pay a duty of
33½ crowns for each slave imported. The kings of Spain and England were
each to receive one-fourth of the profits of the trade, and the Royal
African Company were authorized to import as many slaves as they wished
above the specified number in the first twenty-five years, and to sell
them, except in three ports, at any price they could get.

It is stated that, in the twenty years from 1713 to 1733, fifteen
thousand slaves were annually imported into America by the English, of
whom from one-third to one-half went to the Spanish colonies.[9] To the
company itself the venture proved a financial failure; for during the
years 1729-1750 Parliament assisted the Royal Company by annual grants
which amounted to £90,000,[10] and by 1739 Spain was a creditor to the
extent of £68,000, and threatened to suspend the treaty. The war
interrupted the carrying out of the contract, but the Peace of
Aix-la-Chapelle extended the limit by four years. Finally, October 5,
1750, this privilege was waived for a money consideration paid to
England; the Assiento was ended, and the Royal Company was bankrupt.