This is a book about a cliche; the cliche is unionism's siege mentality. Its is a small book on a large topic; in just eighty-two pages of text, the author seeks to explore the "deep-laid foundations" of the siege mentality in Northern Ireland.

Despite its brevity, this is no tract, but a scholarly and invigorating exploration of the actual events of the siege of Londonderry, the relating of those events, the interpretations placed on them, their commemoration over the years, and the development of "the siege myth".

Along the way, Dr McBride disposes of several other myths. The regular celebration of the events of the siege, in Derry and elsewhere, is not, as has been suggested, a recent product of post-Home Rule unionism, but much older. Nor has the siege been merely a major icon in the Orange calendar; it has had varying significance for different celebrants at different times - a Whig triumph of liberty over a tyrannical crown, in which the Catholic clergy of Derry were happy to join, a Protestant victory for individual conscience over the authoritarianism of Rome, a unionist survival of the worst onslaughts of Irish nationalism.

So what can the Siege of Derry tell us about Ulster Protestant mythology? Dr McBride talks of the "tyrannical hold of the siege myth over Protestant political consciousness". Certainly, the imagery of the siege - the beleaguered community, isolated among hostile forces, under pressure to surrender, fearful of disloyalty within and unsure of outside help - has been repeatedly invoked by Ulster unionists to describe their situation, particularly since the 1886 crisis.

The problem is whether such a view is the unfortunate result of the tyranny of the siege myth, or whether it is a not unreasonable and convenient summary of the real position. Certainly, since 1921 Northern Ireland has been under siege: in 1922, having been legally constituted by London and Dublin, it came under serious military assault from the IRA, was subject to economic boycott, and suffered sustained diplomatic and political attack from both within and without.

Periodic armed assaults from the IRA have continued, as have the political and diplomatic campaigns. Since 1937, the rather antique siege gun of the Constitutional claim has been trained on the besieged. Whether or not one likes Northern Ireland, the fact that it has been under siege from birth cannot seriously be contested. People and places under siege inevitably bear the marks of the siege.

If the siege mentally of unionism is an obstacle to peace and reconciliation - and it is - then the best way to get rid of it is to lift the siege. That is something only others can do. Dr McBride comes close to acknowledging all this, and gently warns his readers against too simplistic an analysis of unionists and the mythologies. But sadly, he cannot resist his own descent into cliche, and a valedictory wish that the ceasefires may create "new opportunities for meaningful dialogue".

This slight tendency to current political correctness appears elsewhere. He warns us that a "present-centred approach" to the writing of history - itself a reaction to revisionism - has its pitfalls and can reduce historiography to just another medium for current ideological debate. It is odd then to find him using a modern, and pejorative term like "hardliners" to describe the apprentices who, in 1689, seized the initiative from their elders. Similarly, the term "British" to describe one side in the 17th-century struggle in Ireland rings false, and "loyalist" has taken on a more precise meaning. The use of the term "armed struggle", without the quotation marks, to describe the terrorism of the past quarter century, is surely a most unfortunate slip.

Dennis Kennedy, a former Dep- uty Editor of The Irish Times, is now an academic attached to the Institute of European Studies at Queen's University, Belfast