Helena

 I am reading what is probably Evelyn Waugh's least characteristic and most nearly forgotten novel, Helena (1950), his sole excursion into the genre of historical fiction – and, oddly, the novel Waugh regarded as his best work. So far, I've found that the most striking thing about it is how un-Wavian it seems: apart from the author's pugnacious Preface, it could have been written by almost any good historical novelist of the time, and I should think very few, reading it 'blind', would guess that it was Waugh. It tells the story of the Dowager Empress Helena, mother of Constantine, who is remembered chiefly for her great pilgrimage to the Holy Land, where she found pieces of the True Cross, and built churches at Bethlehem and Olivet. Otherwise little is known of her life and origins – which gives Waugh scope to build his own version of her biography. Helena is of course elegantly written, and its portrayal of the period of what some historians call the Constantinian Shift – with the great Empire weakened, corrupted and a long way past its great days, and Christianity still inchoate but strangely potent – seems convincing. And there are occasional touches of wit, even satire (it's thought that Waugh's portrayal of Helena's husband, the chilly military careerist Constantius, is based on Bernard Montgomery).
  I particularly enjoyed this passage. Lactantius, the 'Christian Cicero', is talking with Helena, now divorced from Constantius, and Minervina, divorced from Constantine, in the Empress's court at Trèves, where Lactantius is officially tutoring Constantine's son Crispus (who will in due course by killed by his father) ...

'It needs a special quality to be martyr – just as it needs a special quality to be a writer.  Mine is the humbler role, but one must not think it quite valueless ... You see, it is equally possible to give the right form to the wrong thing, and the wrong form to the right thing. Suppose that in years to come, when the Church's troubles seem to be over, there should come an apostate of my own trade, a false historian with the mind of Cicero or Tacitus and the soul of an animal,' and he nodded towards the gibbon who fretted his golden chain and chattered for fruit. 'A man like that might make it his business to write down the martyrs and excuse the persecutors. He might be refuted again and again, but what he wrote would remain in people's minds when the refutations were quite forgotten. That is what style does – it has the Egyptian secret of the embalmers. It is not to be despised.'

What historian could Waugh possibly have had in mind?