ON 17 JULY, the Queen, Supreme Governor of the Church of England, gave Royal Assent to the Marriage (Same Sex Couples) Bill. Thus the Sovereign signed into law a momentous change that had been consistently opposed by a majority in the Church over which she, legally, presides.

Irrespective of where one stands on the Bill itself, or on the Church's (present) teaching on marriage, that event should give pause even to the most tenacious defenders of Establishment. One of their chief arguments is that such a close proximity allows the Church to influence state policy. Or, at least, that it keeps before the state a reminder of a "transcendent authority" standing above it, as Canon Peter Doll argued last month (Comment, 21 June).

But what it has revealed in this case is the state's complete indifference to - indeed, in some mouths, open contempt for - what the Church regards as its wisdom on a crucial element of the common good.

At the General Synod, the Archbishop of Canterbury conceded that the Bishops who spoke on the Bill in the House of Lords were "utterly overwhelmed" by those on the other side.

This latest incident is not, in itself, a conclusive argument against establishment; for this has never implied complete or continuous concord between Church and State on such matters. Nor does the Church's teaching on marriage rank in doctrinal gravity with its beliefs in the Trinity or the incarnation, or in ethical urgency with its stances on absolute poverty, industrial-scale abortion, illegal warfare, or ecological destruction. Many de- fenders of Establishment will thus shrug their shoulders: "Well, we lost this one. Now back to business as usual."

But the symbolism of the Queen's action must raise the question why the Church's proximity to the state is worth clinging on to.

The humiliation suffered by the Church's leadership in this matter comes hard on the heels of the enormous reputational damage done by last year's excruciating imbroglio over women bishops.

Here the issue is not the Church's lack of influence over an important matter of public policy, but the state's continuing capacity to put pressure on it to overturn one of its internal decisions.

We now have the unseemly prospect of the General Synod scurrying around for a workable consensus under the threat of parliamentary override if its "spiritual wisdom" on the subject doesn't line up promptly (in two years, to be precise) with society's.

In this case, of course, it does line up, by and large; but that is irrelevant to whether the Church should defend an arrangement whereby it can be browbeaten into decisions about its internal life. Everyone should be alarmed at the prospect of the Church's coming under pressure from the state to act against its convictions; for those who today might privately welcome the pressure on their Church to endorse a progressive view of marriage or episcopacy might tomorrow lament its being blocked from, say, pursuing a progressive investment policy by a right-wing competition law.

These developments undermine the deeply embedded assumption that the C of E is in some still meaningful, if ineffable, sense the Church "of the nation", and thus obliged to mirror the prevailing morality. Sir Tony Baldry, the Church's official representative in the Commons, put the point succinctly during the debate on women bishops: "If the Church of England wants to be a national Church, then it has to reflect the values of the nation."

I wonder how those who nodded sagely at this view might reconcile it with Paul's injunction: "Do not be conformed to this world, but be transformed" (Romans 12.2).

This same assumption is invoked to justify Parliament's presumed right to press on the C of E the views of many millions who still regard the Church as theirs, even though they neither darken its doors from one year to the next nor remotely recognise the authority of its teachings.

Whatever its imagined legitimacy in the past, establishment is an idea whose time has gone. It is time to acknowledge that the cavernous de facto distance between Church and State now needs to be reflected in a fitting de jure form. Whatever the detailed model proposed, it should seek to recognise Church and State as genuinely independent entities, capable of entering into constructive co-operative relationships, to be sure, but each on its own terms.

The Church should now seize the reins of public debate, and declare that it wishes to extricate itself from what has become an anachronistic and spiritually compromising encumbrance. Such a move would, finally, free the Church from the debilitating posture of constitutional deference imposed on it nearly five centuries ago by a monarch seeking the Church's blessing on a view of marriage that also diverged rather glaringly from its own.

Jonathan Chaplin is Director of the Kirby Laing Institute for Christian Ethics. He writes here in a personal capacity.