Was Mr Justice Coleridge wise to arrange such a very public launch for his Marriage Foundation this week? Whether or not you support its aims - and I do, for reasons I will explain - you may well wonder whether a serving family judge should campaign for one kind of family relationship in preference to another.

It is a question that Sir Paul Coleridge has thought about, of course, and one on which his views are clear.

‘I am convinced that it is now time not only to talk but to act,’ he tells me. ‘Waiting for government or others to take action is merely an excuse for moaning and inactivity. [Saying] "this is not a proper task for the judiciary" is, I feel, another excuse for burying one’s head in the sand. Having considered it fully, I discern no conflict between this activity and the "day job".’

At a time when judges of the High Court and even the Court of Appeal find themselves discouraged at the most senior level from giving media interviews, this is a brave stance to take. Since there are questions about the extent to which the tax and benefits system should favour marriage over the alternatives, it verges on the political. It may mean that Coleridge, a High Court judge for 12 years, will rise no further in the judicial hierarchy. Alternatively, he may be promoted to a court where it is thought he can cause less trouble. Although I would not expect him to discuss his career prospects with me, I know he regards the future of marriage as more important than his future on the bench.

Even so, there is one area where he is shrewd enough to say absolutely nothing. Coyly referred to by the Marriage Foundation as the ‘definition of marriage’, this is the question of whether English law should permit marriage between couples of the same sex.

The foundation says its fundamental concern is family breakdown and the destructive effects this has on the lives of children.

‘One of our primary aims is to reduce the number of children caught up in the family justice system (currently 3.8 million) and the misery which they experience as a result. For obvious reasons those children are almost entirely located within heterosexual partnerships.’

Championing the case for marriage is the best way of ameliorating this problem, the foundation adds, and - in an explanation that is wise if not entirely convincing - it says it does not have the resources to engage in other campaigns. ‘Accordingly we have nothing we want to say in the current debate.’

What, then, is the Marriage Foundation for? Its primary aim is ‘to champion long-lasting, stable relationships within marriage’. More specifically, ‘it will aim to use its independent authority to provide a clear point of reference for the media and in shaping public opinion’. In other words, lobbying. But the foundation is not going to be a ‘cosy club for the smug and self-satisfied of middle England’, its brochure insists. Instead, it hopes to start ‘a national movement to change attitudes from the top to the bottom of society and thus improve the lives of us all, especially children’.

And although the chief rabbi was among those who accepted invitations to speak at the launch on Tuesday evening, Coleridge was determined that the initial impetus should come from solicitors, barristers and judges. ‘Not only are we the ones with the most experience of the effects of family breakdown, but we have made our livelihood from it, as it were, for decades,’ he says.

The problem Coleridge faces is that many lone parents (some of them divorced or bereaved) and many cohabitants (including same-sex couples) regard themselves as perfectly capable of bringing up children. Often, these people are influential in public life. They naturally take the view that their children are better off being brought up by devoted single parents or loving cohabitants than by warring spouses. In individual cases, this may well be true.

But the foundation argues that marriage is a proven route to stronger relationships. The public legal status of marriage is beneficial, both for itself and for the quality of the relationship that it sustains. ‘If we are going to have a happier society, a society where there is greater wellbeing, then the statistics are quite clear: children are best brought up in committed, loving relationships - and the best of these are marriages.’

I promised to declare an interest. Though I cannot count among my forebears the poet who wrote The Rime of the Ancient Mariner or a 19th-century lord chief justice, I feel a certain affinity with this brave judge. We share a birthday (he’s a year older); each of us has been married for some 38 years; and we both have three grandchildren. Above all, we see eye to eye on the importance of stable marriages as the building blocks of society.

I note from its modest brochure that the Marriage Foundation has chosen the keystone as its logo. A keystone stands at the apex of an arch and holds all the other stones in place. It’s wedge-shaped, so it can’t drop out. But if you lift it out of the arch, the smaller stones will inevitably fall to the ground. Divorce lawyers are sometimes to blame for pulling out the keystone.

With nothing to support the smaller stones, family judges then have to pick up the pieces. It is good to find a judge upholding the structures of society, whatever the personal consequences.