Creating the Supreme Court ‘as a result of what appears to have been a last-minute decision over a glass of whisky’ seems to verge on the frivolous, Lord Neuberger tells me.

‘You muck around with a constitution like the British Constitution at your peril, because you do not know what the consequences of any change will be.’

The law lord, who will be taking over as master of the rolls next month instead of joining the new Supreme Court, believes that taking Britain’s final court of appeal out of parliament should have been considered as part of a much wider review. ‘The law of unintended consequences is one of the most reliable pieces of law on the non-existent statute book,’ he adds.

But Lord Turnbull, who was cabinet secretary in 2003 when Tony Blair unexpectedly announced several wide-ranging constitutional reforms, insists that they were not ‘thought up on the back of a fag packet’.

Even so, he admits that the Supreme Court may be more assertive and difficult for a future government than the current law lords – a trend that can be seen already.

Turnbull’s view is endorsed by Lord Falconer, who was appointed lord chancellor to see the reforms through.

‘I believe the effect of there being a Supreme Court will be to strengthen the judiciary in this country,’ he says. Falconer thinks the new court will be bolder, both in vindicating individual freedoms and being willing to take on the executive. The former minister frankly admits that this will lead to problems for future governments.

All three peers were speaking to me for a Radio 4 documentary on the creation of the Supreme Court. The programme, Top Dogs: Britain’s Supreme Court, to be broadcast next week, reveals widely differing views on the court’s likely effect.

Lord Bingham, the former senior law lord and a strong supporter of the Supreme Court, thinks it unlikely that the law lords will behave any differently now that they are no longer in parliament.

‘There is no question whatever of the Justices of the Supreme Court having a rush of blood to the head and saying: "Now we’re free of the constraints of being part of the House of Lords, we can throw our weight around and assert ourselves."’

Bingham’s view is endorsed by the only woman in the new court. ‘I doubt very much whether it will change the way in which we do our work,’ says Lady Hale. ‘Our jurisdiction will be the same, our powers will be the same, we won’t get any greater or grander powers simply by becoming the Supreme Court of the United Kingdom.’

But Lord Collins, the only member of the court to have practised as a solicitor, is less sure. He believes it will evolve gradually into a different type of body – ‘perhaps not as pivotal as the US Supreme Court, but certainly playing a much more central role in the legal system and approaching the American idea of a government of laws and not of men’.

Why should this be? Collins points to the anomalous position of the law lords – peers interpreting legislation that other peers have approved. ‘Once these anomalies are removed, it may be that the court will feel freer to have a more activist role,’ he says.Lord Phillips, who becomes president of the court next month, takes a more cautious approach. On the face of it, he says, the change is one of form rather than substance. The furthest that Phillips will go is to say the move ‘could well prove to be a catalyst for gradual change’. As an example, he says the new court may experiment with majority judgments, something that parliamentary procedure did not permit.

But his deputy believes that having their own building – on the other side of Parliament Square – may not be in the judges’ interests. The law lords used to meet all sorts of people when they walked round the Palace of Westminster, Lord Hope explains. ‘I can’t say our conversation [was] particularly deep, but at least it keeps you in touch with humanity.’

Their rooms in the House of Lords were crammed into a single narrow corridor ‘where interaction is very easy and relationships are extremely good’. In the Supreme Court, the judges will be dispersed around four corners on two floors, ‘so that you have to make an effort actually to go and see somebody’.

Will geography affect the way the court works? Hope says the answer to that is ‘completely unknown’.

And that, of course, is Neuberger’s point. ‘The fact that one might not have designed the system if one was starting from scratch is, to my mind, no argument for saying that, therefore, the system should be changed,’ he explains.

Neuberger fears that the Supreme Court, separated from parliament, ‘could start to become more powerful, to try to assert itself in a way that is... foreign to the British system and would lead to a real risk of confrontation between the judiciary and the legislature, and, indeed, between the judiciary and the executive.’

In his view, there is a real risk of judges arrogating to themselves greater power than they have at the moment.

‘Democratic accountability is fundamental. And while it’s right and proper that judges have independent power and provide a very important balance to the elected legislature and the non-elected executive, it’s dangerous if they get too much power.’

Don’t say you weren’t warned.

  • Top Dogs: Britain’s Supreme Court will be broadcast on BBC Radio 4 on Tuesday 8 September at 8pm and repeated the following Sunday.