 Dewar became the gunnery officer of the armoured cruiser Kent on 24 August 1905, where he remained until 1908. Dewar's dedication and standard of training became evident when his ship led the Fleet in battle practice firings and gunlayer's-test. He was reassigned to Excellent on 19 January 1908 for instruction duties. Soon he was sent to sea again, being made gunnery officer of the battleship Prince George on 8 February 1908. He rejoined Excellent on 22 December that year. On 11 June 1909 Dewar was "lent" as gunnery officer to the protected cruiser Spartiate for the annual fleet manœuvres. Once the manœuvres were finished, Dewar was made assistant to the Inspector of Target Practice, an important gunnery position at the Admiralty on 17 July. In the same year, he was asked to lecture on the Imperial Japanese Navy, which he had previously had experience of, at the Royal Naval War College at Portsmouth. During his talk, he exhibited an unpalatable forthrightness by saying that the Royal Navy needed more intellectual officers like Togo Heihachiro, implying that there was a dearth of such officers. The President of the College, Lewis Bayly, abruptly terminated his lecture.
