Historians have always known that Evangelicalism got into the navy because it is linked with one of the most dramatic – and notorious – episodes of the Napoleonic Wars. In 1809 a British fleet had the French at their mercy in Aix Roads and might have destroyed the entire battle squadron as it lay stranded and keeling over in shoal water – had the Evangelical commander-in-chief, Lord Gambier, shown as much concern for winning the war as for spreading his religion. That was the opinion expressed fiercely and publicly by Lord Cochrane, the young captain of genius who had personally created the opportunity for victory. The echoes of that argument have reverberated to the present, with Gambier invariably seen as an eccentric who might have made a bishop but was incompetent as a fighting admiral.

The navy never seemed the right place for evangelical fervour – religion maybe, but not zealotry – and during the Revolutionary and Napoleonic Wars officers with these opinions were commonly seen as misfits, with enough collective identity to earn the pejorative ‘Blue Lights’. Gambier, the best known of them, by missing his call to greatness at Aix Roads showed that he was unsuited for command, while his family link with the able but unpopular Sir Charles Middleton (later Lord Barham, First Lord in 1805–6) invites the conclusion that eminence came through nepotism not ability. Religion of this kind – so the line runs – should have stayed in pulpits ashore: afloat it was risibly irrelevant and damaging.

And yet there is something astray with this evaluation. For a start, it under-estimates the strength of religious practice in the navy. While Jervis was more of a martinet than a pastor he was scarcely less zealous than Gambier in holding church services at sea even in the presence of the enemy. Nelson's Christianity was not Gambier's, but it fed an essential part of his persona. Neither Jervis nor Nelson were Blue Lights, but Nelson was just as ready as they to invoke the aid of the Almighty and to attribute victory to his intervention. All three of the British flag officers at Trafalgar were supporters of the Bible societies and distributed religious literature to their crews – just as Gambier is so slated for doing.