Not that the book is a gloomy read. Anyone who has ridden with Norwich through his previous tumultuous volumes will remount with pleasure for this last hack home. The pace is easy as always, and as we pass among the spectacularly varied scenes of war, intrigue, theological debate, marital kerfuffle, sacrifice, revenge, blazing ambition and lordly pride, our guide calms our passions with an infinity of curious asides and grace notes. lt is history of an old-school, gentlemanly kind - no gimmicks, no show-off vocabulary, just a grand story told with true grandeur.
The narrative is unashamedly partisan. Lord Norwich vehemently disagrees with Edmund Gibbon about the nature of Byzantium ("base and despicable"), partly because he considers it a genuinely holy organism, but chiefly perhaps because he so loves its art, its architecture and its learned culture - he believes the Anastasis fresco in the church of St Saviour in Chora in Istanbul to be "perhaps the supreme masterpiece of all Christian art". During the four centuries covered by this volume, the Byzantine Empire was almost incessantly under attack, from fellow-Christians as from infidels; I very soon fell into the author's habit of cheering on the Byzantines. The Muslims don't sound so bad, but the vulgar forces of the Catholic west, with their greedy half-literate princes and their arrogant Popes, storm and squabble down the generations like a pack of street-thugs.
I simplify, of course. The drama of Byzantium's decline is nightmarishly complex, with its constantly shifting cast of Bulgarians, Angevins, Seljuks, Germans, Bogomils, Pechenegs, Catalans, Turks, Sicilians, Mongols and hairy nomads. Norwich simply presents us with the facts, logically, chronologically, together with maps, genealogical tables and an apparently never-flagging zest. He can be forgiven for lifting, now and then, substantial chunks from his previous major histories of Venice and Norman Sicily: the wonder is that he manages to lead us through these historical tangles without ever once, not for a moment, being a bore.
Even the esoteric theological differences which so disastrously divided eastern and western Christianity are explained with clarity and patience: the filoque controversy, for instance, concerned with the question of whether the Holy Ghost proceeded from both the Father and the Son, or from the Father only; or still more obscurely, the matter of the Hesychasts, and whether they could in fact, by techniques of meditation, see for themselves the divine light of the Transfiguration. In less fastidious hands these disputes could be incomprehensible or preposterous. Norwich makes of them interesting matters of politics as of faith.
Mind you, just occasionally the convolutions really are rather comical. I was nagged by a feeling of deja vu when I read the footnote on page 263 warning us that the city of Magnesia mentioned in the text was "not Magnesia ad Sipylum, the modern town of Manisa near Izmir, but Magnesia on the Meander, some thirty kilometres east of Kusadasi: until I remembered a note in one of Beachcomber's columns years ago to the effect that the M'Hoho mentioned in a Colonial Office report was not the M'Hoho near Zumzum, but the M'Hoho near Wodgi.
Lord Norwich will not resent the reference. His tragic story is enlivened everywhere with humour and surprise. Besides the towering figures at the centre of the narrative, the Emperors, the scholars, the theologians, the generals, a host of fascinating lesser characters is sighted along the way. There is Bolkan the Zhupan of Rascia. There is Hunyadi the Voyevod of Transylvania. There is the unfortunate princess Adelaide of Brunswick- Grubenhagen, brought all the way to Constantinople, poor soul, to wed the future Andronicus III, and conclusively dismissed as "a German lady of insufferable tedium". Fifty-eight men called John complicate the index of this book, including nine Emperors, four Popes, three Tsars, five Patriarchs, two Despots, an ex-King of Jerusalem and John the Bastard of Thessaly.
But however amused and intrigued he is himself by this wild profusion, Norwich never loses sight of his great theme. We know from the start that Byzantium is doomed. For 400 years the Byzantines struggle to survive, harassed on all sides by Christians and Muslims alike, sometimes achieving victories, sometimes postponing disasters, but irretrievably weakening down the generations. The spectacle suggests the slow sinking of some mighty and indomitable battleship, fighting to the last, flaming in the dark as her magazines explode, her steering falls and the shells fall like waterspouts all about her.
Cynics might say that nothing so became Byzantium as its fall the 55 days of heroic resistance to the Sultan Mehmet II which ended with the last of the Emperors, Constantine IX, disappearing for ever from the battle as from history. "Byzantine" has become a word more often pejorative than admiring, and the notion of Constantinople as a heroic bulwark of Christian values is generally familiar only to the Greeks - to this day Tuesday is an unlucky day throughout the Hellenic world. Lord Norwich has taken upon himself to straighten the record, and to give the martyrdom of Byzantium its proper place in European history.
What he has done too, for me anyway, is to translate a dream into literary substance. The idea of Byzantium has haunted the western imagination for generations, but for most of us it has been hardly more than a drifting fantasy - a lovely arch or a lyrical mosaic, a dazzle of Klimt, a snatch of Yeats. Norwich's great trilogy has dispersed none of this magic, but has given it humanity too. Mehmet the Conqueror and Khaireddin the Torch of the Faith, the Palaeologi and the Hesychasts, in these pages we recognize them as fallible human beings after all, just like you and me.
Well, a bit like you and me...
Above: the Anastasis fresco in the church of St Saviour in Chora, Istanbul, 'perhaps the supreme masterpiece of all Christian art'