Sir Michael has been rewarded for the eight years he spent shaping the Government’s public-sector reform agenda, first for David Blunkett, the former education secretary and then for Tony Blair.

He will leave his post as head of the Prime Minister’s delivery unit in July to take a job with McKinsey, a consultancy firm with close links to the Government.

Best known as the man behind the primary literacy and numeracy targets, Sir Michael, 49, became notorious for his flow charts and diagrams showing his latest thinking about the state of the education system.

Despite his close identification with the new Labour project, Sir Michael - who has been described as looking like a revolutionary in need of a good meal - was not always on the side of the Government.

The former history teacher cut his political teeth as education officer of the National Union of Teachers between 1989 and 1993, a time when the union was fiercely opposing the introduction of national tests.

After short spells as a professor of education at Keele university and London university’s Institute of Education, Sir Michael was new Labour’s choice as the pound;100,000-a-year head of the newly-created standards and effectiveness unit at the Department for Education and Skills.

Initial rapid progress towards the targets, 80 per cent of 11-year-olds reaching the expected level in English and 75 per cent in maths by 2002, made primary education one the of the major success stories of Labour’s first term.

But progress stalled, the initial targets have still not been met and this failure contributed to the resignation of Estelle Morris, Mr Blunkett’s successor. By then, however, the man described by Mr Blair as “one of the most stimulating thinkers in British education” had moved on to bigger things. But after his move to the Prime Minister’s delivery unit, where he was in charge of monitoring targets and progress across the whole public sector, Sir Michael kept a lower public profile - perhaps learning from earlier painful experiences.

He was criticised for ignoring state schools in Hackney, north London and sending his daughters to private school. And in 1998, he had to seek sanctuary from the press in a hotel room after he told headteachers “we are living in a post-Christian society”.

Sir Michael has been a robust defender of the school accountability culture. He said: “What people often miss is the fact that ministers are made accountable like everyone else. David Blunkett was the first secretary of state to be judged by how well pupils did in schools and that will be true of everyone of his successors. That is a massive step forward.”

For his former union colleagues the move to McKinsey will be the final sell-out.

But they should not be surprised. The close links between McKinsey and Number 10 were shown by the recent appointment of David Bennett, a former McKinsey partner, as head of the Downing Street policy unit.

It may be a match made in heaven. The company’s philosophy? “Everything can be measured and what gets measured gets managed.”