For a body that exists to promote reform of the law, the Law Commission has surprisingly little legislation that it can call its own. There is little more than a statute enacted in 1965, setting up a body to review the law ‘with a view to its systematic development... simplification and modernisation’.

Last month, though, parliament passed the Law Commission Act 2009, which takes effect in January. Its existence is a tribute to the skilful behind-the scenes manoeuvring of Sir Terence Etherton, who retired in the summer as chairman of the Law Commission and returned to the bench with a seat on the Court of Appeal.

His first achievement was to persuade the Ministry of Justice that legislative reforms would make the Law Commission more effective. But when it became clear that the government’s preferred legislative vehicle – the Constitutional Reform and Governance Bill – would not become law before next spring at the earliest, Etherton had the idea of hiving off the reforms into a private member’s bill which, with government support, became law sooner.

What the 2009 act does is to require the lord chancellor to tell parliament every year whether the government has decided not to implement any of the previous year’s crop of Law Commission proposals – and if not, why not. The idea, of course, is to hold ministers to account if they allow proposals to gather dust.

That has certainly happened in the past. The commission’s recommendations for reforming the restrictions in trusts law against perpetuities and excessive accumulations were published more than a decade before being implemented last month. Even then, I suspect the Perpetuities and Accumulations Act 2009 would never have become law without the support of experimental parliamentary procedures under which non-controversial bills need not be debated on the floor of either house.

The new Law Commission Act also allows commissioners and ministers to agree a statement – which will be known, in the current fashion, as a ‘protocol’ – setting out what the commission is to do, how it will co-operate with the government and how its proposals are to be treated.

Sir James Munby, who took over from Etherton as chairman in the autumn, said his predecessor had achieved ‘considerable improvements in our relations with government’. These reforms gave Munby ‘much more optimism than chairmen have had for a decade or more that the commission’s proposals would be implemented; and sooner rather than later’.

Ministers now acknowledged that far too many Law Commission reports had been sitting on the shelf for far too long, the new chairman explained. ‘There is now, I sense, a real will to tackle the legacy programme of unimplemented reports.’

Another improvement that Etherton had achieved was a convention that the chairman would be made a lord justice of appeal on appointment rather than on retirement. That gave the job greater status, Munby said, though it was not the reason he applied for it.

‘It is one of the most interesting, fascinating and important jobs that one can aspire to,’ he explained in an interview with the Gazette. ‘It enables one to do things to promote the development of the law which one can’t do as a judge.’

More than two years ago, the Law Commission recommended that qualifying cohabitants should be given new remedies on the breakdown of a relationship. The government has deferred a decision until it has assessed the effect of similar reforms in Scotland. Meanwhile, a more recent paper from the commission has proposed reforming the intestacy rules so that a surviving cohabitant could share in a partner’s estate without having to go to court. Munby has considerable experience of these issues.

‘Anybody who has practised in those areas of the law knows that the problem of, typically, the woman at the end of what may be a very long and very stable relationship not sanctified by marriage is, in financial and economic terms, desperate.’

Referring to the ‘undying myth of the common law marriage’, Munby said that ‘astonishing numbers of people’ believed they had some kind of protection on the breakdown of a long-time relationship.

‘One view is that the solution to this problem is education. But 35 years of attempts at education seem to have had no effect at all. Taking a pragmatic view reflecting the realities of the society in which we live – and taking a principled view of the need to avoid injustice – I see nothing unprincipled or objectionable in the views expressed by the commission.’

The new chairman did not think the reforms would undermine marriage. ‘Lawyers – and I would have thought the Law Commission as well as the judges – must have regard to the society in which we live. It is a fact that our society has changed immensely in some respects, even in the time that I have been a practising lawyer.’

Looking ahead, Munby promised a consultation paper next summer on whether pre-nuptial agreements should be made enforceable in England and Wales. ‘I have quite an open mind on this,’ he said.

In many of these issues, I suggested, it was a question of whether the law should follow society or lead it.

‘The answer has to be more nuanced,’ he said. If we simply followed society we would legalise shoplifting on the basis that it was endemic. ‘On the other hand, the time has long since gone when it was the business of the judges to enforce morality.’

Ultimately, though, Munby has influence without power. The Law Commission can make recommendations, as he says, but decisions are for parliament to take.