Visual Arts: Here are a number of indisputable facts about the Bayeux Tapestry: it is 68.38 metres long and varies in width from 45.7 centimetres to 53.6 centimetres; within these dimensions are shown 626 people, 202 horses or mules, 55 dogs, 505 animals of all kinds, 37 fortresses or buildings, and 41 ships or boats.
One other important piece of information needs to be given: the Bayeux Tapestry is not, actually, a tapestry. It is made of eight strips of woven linen stitched together and all of them covered in embroidery using five different coloured threads.
And after that even Sir David Wilson, former Director of the British Museum and an acknowledged expert on the period in which the so-called tapestry was produced, cannot state categorically that he is able to confirm more. No one, for example, knows for sure who was responsible for all that fine stitching, nor when, where or even why it was undertaken. What was the purpose or function of the finished work? Probably to provide decoration for a private home, possibly that of Odo, Bishop of Bayeux and half-brother of William, Duke of Normandy and, following his victory at the Battle of Hastings in October 1066, King of England.
It is William's triumph on that occasion that the Bayeux Tapestry not only narrates and celebrates, but also seeks to justify. William - illegitimate, incidentally, and therefore liable to have his right of sovereignty questioned even in Normandy - had a fairly tenuous claim on the English throne. But so too did Harold, Earl of Wessex until his coronation in January 1066 following the death of King Edward the Confessor. Even before attempting to face off the Norman challenge to his authority, Harold had already been required to put down two other threats, one of them - from Harald of Norway - just weeks before Hastings.
The Bayeux Tapestry relates some, but not all, of this previous history. The narrative it offers is highly informative (sometimes in ways that could not have been imagined at the time of manufacture) but just as intensively selective. And the story presented along the tapestry's length cannot be verified in all circumstances due to the inadequacy of alternative source material. There are a number of written documents from the period that include information on William, Harold, Edward and the other main players, but not enough of them and not consistent in their details. As the four New Testament Gospels illustrate, this is a quandary familiar to all interested historians: dealing with an assumption of understanding made by earlier chroniclers who cannot hope to appreciate what will and will not be subsequent gaps in the story they have chosen to tell.
In the case of the Bayeux Tapestry, some of the gaps are tantalising. Who is the woman called Aelfgyva shown relatively early in the work and who is the unnamed man who lays his hand against her cheek? Similarly, who is the dwarf called Turold being carried in a sling? Was he so well-known in the 11th century that no further explanation for his appearance was required by viewers? Did Harold swear an oath of fealty to William in Normandy while Edward the Confessor was still alive, and at Hastings did he really die after being struck in one eye by an arrow? Both of these incidents are shown on the Bayeux Tapestry but the precise nature of Harold's connections with the Norman Duke prior to 1066, as well as the manner of his death in that year, remain unmentioned by other extant contemporary material. So, unless some remarkable new documentation on the Battle of Hastings and the Norman Conquest is discovered - an unlikely scenario - answers to these and many similar questions will never be found.
Instead, the Bayeux Tapestry must remain a fascinating and unique insight into the ways in which some of our forebears lived almost a thousand years ago. This beautifully illustrated book provides an admirable means of enjoying that insight.
• Robert O'Byrne is a writer and journalist. His most recent book, Living in Dublin, was published last autumn