History testifies to the truth that the Presbyterian tradition is not an independent Reformed tradition, but rather represents a non-conforming tradition within the Protestant Episcopalianism from which it sprung. At the close of the initial 16th century reformation the whole of the British Isles was Episcopalian, there being bishops in the Churches of England, Scotland, and Ireland. It was not until the beginning of what historians call “The Long Eighteenth Century”, a period well beyond the Protestant Reformation, that the episcopate was finally disestablished in one of the three Kingdoms.
Presbyterianism arising as it does by a partial departure of the earlier Protestantism established within Great Britain and Ireland during the Protestant Reformation of the 16th century, in some respects it represents an apostasy from the Confessionally Reformed faith, while in other respects it represents a continuation of it.
A great article from the Protestant Association, check out the original article here.