The Wealth of Nations by Part 4 Chapter 6 Page 6

But if at any time this deduction or abatement of customs, which is to be made as aforesaid, shall in any manner be attempted and prejudiced, it shall be just and lawful for his sacred royal majesty of Portugal, again to prohibit the woollen cloths, and the rest of the British woollen manufactures.

Art. III.

The most excellent lords the plenipotentiaries promise and take upon themselves, that their above named masters shall ratify this treaty; and within the space of two months the ratifications shall be exchanged.

By this treaty the crown of Portugal becomes bound to admit the English woollens upon the same footing as before the prohibition; that is, not to raise the duties which had been paid before that time.