In method we have, instead of an attack with the two main divisions, an attack with one only, with the other covering it.

In intention we have as the primary function of the reserve squadron, its attachment to one or other of the other two main divisions as circumstances may dictate.
The natural inference from these important changes is that Nelson's conception was now an attack in two divisions of different strength, the stronger of which, as the memorandum subsequently explains, was to be used as a containing force to cover the attack of the other, and except that the balance of the two divisions was reversed, this is practically just what Clerk of Eldin had recommended and what actually happened in the battle.

It is a clear advance upon the original idea as explained to Keats, in which the third squadron was to be used on the primitive and indefinite plan of De Chaves and Lord Lisle as a general reserve.

It also explains Nelson's covering letter to Collingwood, in which he seems to convey to his colleague that the pith of his plan was an attack in two divisions, and, within the general lines of the design, complete freedom of action for the second in command.

How largely this idea of independent control entered into the 'Nelson touch' we may judge from the fact that it is emphasised in no less than three distinct paragraphs of the memorandum.
Such, then, is the fundamental principle of the memorandum as enunciated in its opening paragraphs.