Sentencing law is hell. Not my expression but one used by a former president of the Supreme Court in a case called Noone. It was about the law on consecutive prison sentences – which counsel had needed nearly five hours to explain when the case came before Mr Justice Mitting in 2008.

‘The road to hell is paved with good intentions,’ said Lord Phillips when Noone reached the Supreme Court in 2010. ‘Hell is a fair description of the problem of statutory interpretation caused by transitional provisions introduced when “custody plus” had to be put on hold because the resources needed to implement the scheme did not exist.’ Lord Judge thought it ‘outrageous’ that so much time and effort was needed to find a way through the ‘legislative morass’ and work out the prisoner’s release date.

Wouldn’t it be heavenly to cut a clean sweep through that morass and build a new sentencing code for England and Wales? Instead of having to search through 1,300 pages of legislation dating back to 1361, we could always find the applicable sentencing law by consulting a single act of parliament.

Impossible? Not according to the Law Commission. Very cautiously, the government’s law reform advisers slipped out a draft sentencing bill just before the summer holidays. It is open for consultation until early next year.

Though nothing like the size of the legislation it would replace, this is a huge bill: 285 clauses, 18 schedules, more than 250 pages. How could a minority government hope to get it through a normal parliament, let alone one swamped by Brexit legislation?

The answer is to treat it as a consolidation bill. These bring together existing acts of parliament without changing the law – although they may contain minor corrections and drafting improvements. Once a consolidation bill has been approved by a joint select committee of MPs and peers, it generally gets through both houses of parliament with very little time spent on debate.

But a consolidation bill cannot be used to make policy changes or even to codify the common law. And yet some substantive changes would be needed to pave the way for the planned new Sentencing Act. So the commission needs the government to add a couple of short clauses to a separate justice bill.

One of those clauses would streamline the law ahead of consolidation. The other is a radical move to solve the ‘hell’ problem: working out which version of the law is in force at the relevant time.

We all know that acts of parliament are not normally brought into effect on the day they are passed. Sentencing reforms are often given effect by statutory instruments issued months or years later. Sometimes, the changes are given only partial effect or not brought into effect at all. But they are not normally retrospective: if an offence was committed before a new law is brought into effect, the old law usually applies. Because they may be needed for historical cases, the earlier laws are not repealed. Over time, there may be many layers of old law that have been saved in this way.

There would be little point in the commission’s consolidation bill if courts had to consult previous acts of parliament when sentencing for offences that were committed before it took effect. So the unique selling point of the sentencing code is that it will effectively sweep away all the old law on sentencing, with only limited exceptions. The new act will apply to all convictions after it is brought into force. Because the ‘clean sweep’ clause changes the substantive law, it needs to be in the pre-consolidation bill along with the streamlining changes.

The way in which this must be done is highly technical for reasons that I will not attempt to summarise and the courts do not need to understand. What is important is that offenders will not face higher sentences under the code than they would have received under the old law. The code does not create or extend minimum sentences. Nor does it replace sentencing guidelines or reduce judicial discretion.

The commission’s ambitions do not stop there. It wants all future sentencing reforms to be implementing by amending the code. Ideally, they would take effect for all offenders at the same time. At the very least, it should be possible for anyone to see from the legislation website maintained by the National Archives whether a particular sentence is available for an offence committed on a particular date. There would be no need to work through the statutory instruments.

Enacting the sentencing code would bring huge benefits. The commission estimates that it would save over £250m in court costs over the next decade. But the ultimate prize is in making sentencing law so clear that it can be understood by everybody – even judges.