In less than a month’s time, we shall be marking the 10th anniversary of a constitutional revolution. It will not be a cause for celebration. On June 12, 2003, the judiciary lost its head. In sacking Lord Irvine of Lairg, Tony Blair was not merely reshuffling his cabinet. The prime minister was deposing the lord chancellor, at that point arguably the most influential figure in the land. Would the legal profession now be fighting for its future if it still had cabinet support from a minister who was not only a former lawyer but also the country’s most senior judge?

How all this came about was, for six years, one of the great political mysteries. Irvine is one of the few ministers not to have published his memoirs. He declined all interviews. But in 2009 he was provoked into responding to Lord Turnbull, who had been cabinet secretary at the time of the lord chancellor’s demise. Turnbull had told the House of Lords constitution committee that Irvine was consulted before the decision was taken to abolish his role. ‘The trouble was that he disagreed with it,’ Turnbull asserted. The former lord chancellor responded with a memorandum of his own which was published by the committee in January 2010, together with a little-noticed rejoinder from Blair himself.

Irvine tells us he had read press rumours that his post was to be abolished. Were these true? Blair told him on 5 June 2003 that no decision had been taken. He asked the prime minister how a decision of this magnitude could be taken without consulting those affected. ‘The prime minister appeared mystified,’ Irvine recalled, ‘and said that these machinery of government changes always had to be carried into effect in a way that precluded such discussion because of the risk of leaks’. Irvine left Downing Street surprised that Blair thought abolishing the office of lord chancellor was similar to a routine transfer of departmental responsibilities. He was also surprised that ‘the prime minister had no appreciation that the abolition of this office of state, with a critical role in our unwritten constitution… required extensive consultation, most careful preparation and primary legislation’.

When the two men met again the following Monday, Irvine concluded that Blair had not received proper advice from officials. At that stage, Blair had simply been planning to transfer Irvine’s responsibilities to Peter Hain, who was to sit in the Commons as secretary of state for constitutional affairs. In that case, said Irvine, Blair would have lost an opportunity to restructure the system, transferring responsibility for criminal law and procedure to a new ministry of justice. The next day, Irvine told the prime minister, in writing, that the whole process had been botched. ‘The lord chancellor as head of the judiciary is presently the central organising principle of the administration of justice in the country, and that is being swept aside without any assessment of its value.’

Irvine told Blair it was not too late to set up a proper ministry of justice headed by a Commons minister. He offered to see it through ‘and bow out on its completion’, elaborating on his offer in a written note to Blair the next day. ‘This alternative proposition was, I understand, rejected after cabinet on Thursday 12 June 2003,’ Irvine recalled in 2009. ‘That afternoon I returned the great seal to Her Majesty and ceased to be a member of the government.’ Blair set up a department for constitutional affairs headed by Lord Falconer.

Turnbull had little to say on the subject in 2009. But his successor as cabinet secretary, Sir Gus O’Donnell, insisted that the prime minister had been properly advised and that Irvine’s officials had been consulted. Blair himself told the committee that giving the lord chancellor’s political functions to a politician was an ‘obvious modernisation’. In a letter sent at the end of 2009, the former prime minister acknowledged that Irvine would have implemented the reforms if asked.

‘However, I felt, as his memorandum implies, he was unsympathetic to my desire to change the lord chancellor position,’ Blair wrote. ‘So I thought it right to make a change of person as well as a change to the office. It is correct that I could have retained him in government to see through the change and then leave; but I thought it better to have the process of change led by someone [who] was then going to be part of it.’

Turning the lord chancellor into just another politician was indeed an obvious modernisation – and one I used to favour. But its disadvantages are all too obvious now. The lord chancellor had evolved over the centuries into a uniquely valuable constitutional pivot. Wrenching it out of the system a decade ago was not a wise thing to do.