It had gone. There could be no doubt about that. Cecilia Plumridge, the Assistant Librarian, opened the Muniment Room at 8.30am. Nothing was unusual. There was no indication of a forced entry. The alarm system, which had been properly set the previous night by her own hand, had not been activated. The armour-plated glass case, with its thirty-eight locks – one for each Primate of the Anglican Communion – appeared to be untouched. And yet its contents had vanished.

Miss Plumridge was not a superstitious woman. Had she been so, she would have attributed the theft to the powers of Faerie or the powers of Darkness. But the work of sprites or demons in the official residence of the Archbishop of Canterbury was clearly unthinkable. Instead, she forbore to speculate and rang the Metropolitan Police.

Within half an hour the place was alive with uniformed constables young enough to be her children, and laddish Detective Constables with gel in their hair and loud ties from Next. Miss Plumridge reacted to the excitement by withdrawing to the carrel at the end of the Library which she had fitted out with a cordless electric kettle and a two slice toaster. There she made herself a cup of tea and awaited the unfolding events. George and Eileen, mercifully, were on a visit to indigenous Anglican congregations in Patagonia. The matter would no doubt be capably dealt with by Canon Frazer Guildenthal, the Archbishop’s Officer for Anglican Communion Affairs.

Guildenthal, a portly American of German Lutheran extraction, arrived swiftly on the scene. He was quite obviously more at home with laddish constables than Miss Plumridge. Indeed, he owned a number of eventful ties himself.

‘What exactly’, asked a personable young policeman, ‘is missing?’

‘How can I explain?’ began the Canon.’ It is… an invaluable treasure, a unique document… it is to Anglican Ecclesiology what the Rosetta Stone is to Egyptology… what Magna Carta is to parliamentary democracy.’

The young man, whose pre-Hendon education had been entirely within the curiously misnamed comprehensive system, was understandably puzzled. Runnymede and the Napoleonic campaign of 1798 were a closed book to him. Canon Guildenthal continued expansively. Lambeth Conferences, Essays and Reviews, Bishop Colenso; all tripped gaily off his tongue. The young man determined to take the bull by the horns.

‘So am I to understand that this Quadrilateral thing, which until this morning was housed in this glass case, is just a scrap of paper?’

‘A piece of paper certainly,’ relied Guildenthal, ‘but so much more than that: a focus of unity, a symbol in every sense of the word. Reputations have been lost and wars fought, you know, over a mere scrap of paper. Think of Chamberlain.’

* * *

Commander Eve Melhuilish’s distinctive period sports Bugatti purred to a standstill in the ivy-clad courtyard of Lambeth Palace. This she knew would be the defining case of her career. Melhuilish was not your run-of-the-mill policeperson. She had studiously avoided the Lynda la Plante stereotypes. Educated at Somerville and St Stephen’s House she had received her call to police work whilst preparing for the priesthood of the Church of England. Her father, a former Dean of Wells, had been bitterly disappointed.

Would the old man have changed his mind now, she wondered, as she leapt out of the open-topped motor onto the springy turf? Would he be proud that a daughter of his had been called in by Lambeth Palace to solve the mysterious theft of the Lambeth Quadrilateral?

Dafyd Williams, the Bishop-at-Lambeth, oozed towards her over the well-raked gravel. Eve knew him from his visits to her father at Morden College during his retirement. She received the celebrated boneless handshake and was led up the steps, past the awful full-length portrait of Robert Runcie (looking, she thought, more like a pantomime dame than an archbishop), to the waiting Guildenthal.

‘Guilders!’ exclaimed Eve, as she turned the corner into a rather dull room full of portraits of unremembered clerics, ‘what in the world are you doing here?’ Commander Melhuilish knew Canon Guildenthal from her days as an exchange student at General Theological Seminary, when Frazer and his friend Gino had been the life and soul of the party (and of much else besides).

‘Holding the Anglican Communion together,’ said Guildenthal, without a trace of embarrassment, ‘spinning for Jesus, as one might say.’

‘You put more trust in his concern for that institution than I do,’ relied the Commander. She had traded in her Anglican loyalty card at the same moment as she had determined to be a first-rate sleuth. No loyalties; no ideals; no ideological baggage. All that was left now from her time at St Stephen’s House was a quirky interest in ecclesiastical haberdashery, and the obligatory copy of Unguarded Hours.

‘So fill me in on this one. What precisely has been taken, and what value would it be to anyone?’

‘Together with Richard Hooker’s three-legged stool, which is now permanently housed at the V&A next to the Great Bed of Ware,’ intoned Guildenthal, ‘the Lambeth Quadrilateral is the most precious relic of Anglicanism. They are about as close as a Communion made up of three warring theological factions has ever come to credal solidarity. But, I think it would be true to say that the Quadrilateral no longer occupies the place it once did.’

‘You can say that again,’ said Melhuilish, pulling on the plastic gloves and examining the locks on the empty display case. She was impatient with this ponderous recitation of what she already knew. ‘But who would want to steal it? Who has an interest in wiping the slate clean of that particular part of the common past?’

‘Almost everyone,’ replied Guildenthal. ‘Being an Anglican is a messy business at present – more fractious than the Mujahadin.’

Theological terrorism! Somehow the notion appealed to the Commander. She had come to see the Church of England as the Laodicea of the ecumenical spectrum. It was heartening to think of a bunch of Anglican desperadoes caring about anything with sufficient passion to be both decisive and effective. Those were not, it had to be admitted, characteristics which were usually associated with the clergy. When groups of Christians get round to hating one another, she reflected, you can at least be sure that they are taking their religion seriously.

With that Melhuilish returned to the Bugatti and, to the sound of Buxtehude’s cantata Quemadmodum desiderat cervus, she swept out of the narrow confines of that sequestered quadrangle, across Lambeth Bridge and into the reassuring secularity of the Horseferry Road. She was on her way to visit Ben, the six foot, rugby-playing counter tenor who shared her life. Her heart too could pant.

The flat in Ambrosden Avenue was untidy as ever. Eve poured herself a single malt, curled up on the vast squashy sofa, and turned on Radio Three for company. Ben, she was sure, would not be long. The glib, well-researched chatter of Humphrey Carpenter overwhelmed the silence, and she found herself drifting into a strange quasi-theological reverie. Stephen Sykes and Paul Avis were two bespectacled schoolboys competing in an egg and spoon race for the prize of being considered the most Anglican of them all, whilst the Headmaster (a curious amalgam of Michael Ramsey and Donald Sinden) was playing Scrabble with Joseph Ratzinger. She was asleep in no time at all.