The basis of the new tactical code was no longer the Fighting Instructions, but the Signal Book.

Signals were no longer included in the Instructions, and the Instructions sank to the secondary place of being 'explanatory' to the Signal Book.[1] The earliest form in which these new 'Explanatory Instructions' are known is a printed volume in the Admiralty Library containing a complete set of Fleet Instructions, and entitled 'Instructions for the conduct of ships of war explanatory of and relative to the Signals contained in the Signal Book herewith delivered.' The Signal Book is with it.[2] Neither volume bears any date, but both are in the old folio form which had been traditional since the seventeenth century.

They are therefore presumably earlier than 1790 when the well-known quarto form first came into use, and as we shall see from internal evidence they cannot have been earlier than 1782.

Nor is there any direct evidence that they are the work of Lord Howe, but the 'significations' of the signals bear unmistakable marks of his involved and cumbrous style, and the code itself closely resembles that he used during the Great War.

With these indications to guide us there is little difficulty in fixing with practical certainty both date and authorship from external sources.[3] In a pamphlet published by Admiral Sir Charles Henry Knowles in 1830, when he was a very old man, he claims to have invented the new code of numerical signals which Howe adopted.