In 1666 Prince Rupert and George Monck, Duke of Albemarle were appointed by Charles II to a joint command of the fleet that had been engaged in the Second Dutch War, fought largely at sea, for five years without either side gaining much advantage.

The appointment of two men to share a single responsibility is a risky thing to do at the best of times and, on the face of it, appointing such contrasting characters as Rupert and Monck appeared to be asking for trouble; but the King was a shrewd judge of men, he knew his dashing – at times impetuous – nephew well and had known Albemarle since the latter had been instrumental in bringing about the Restoration. Both were long serving soldiers with considerable seagoing experience and both were accomplished organisers of military affairs; they had known each other for some years and it is fair to assume that they respected each others capabilities.

The letters themselves give a strong indication of harmonious co-operation. The pair, particularly Albemarle, had a significant influence of the development of naval battle tactics. This period saw the genesis of the method of fighting fleet actions in a ‘line of battle’ that was to persist right up to Jutland in 1916.

At the time that Albemarle took command of the fleet, naval battles were conducted as a general mêlée but he applied a soldier’s orderly approach to disposing of forces for a land battle and in 1653 he had laid down instructions for fighting in line.

The letters give an insight into how the new naval administration being put together by the Duke of York and Samuel Pepys was developing. There were familiar problems with pay, victualling and the quality of ship construction but these may be seen as largely the natural result of a rapidly expanding organisation.