He was a defence lawyer who had represented Irish republicans and Islamists in terrorist cases. Along with Cherie Booth, QC, the Prime Minister’s wife, he had been a founder of Matrix Chambers, the human rights set.

The Tories cried foul. They said it was astonishing that a Blair crony who had never prosecuted a case in his life should become Director of Public Prosecutions.

But it is now widely accepted that Mr Macdonald is transforming the CPS.

Prosecutors now engage with police from the beginning of big inquiries to ensure the smoothest passage to court. There is more rigorous testing of evidence — and engagement with victims and witnesses — before cases get to trial.

Mr Macdonald has called for enhanced powers to pursue terrorist cases, sent “flying prosecutors” to Germany to gather evidence against World Cup hooligans and accrued a collection of legal tools under the Serious and Organised Crime Act 2005.

With 25 years’ experience as a defence barrister, Mr Macdonald seemed to know the weaknesses of the CPS. It was a classic case of poacher turned gamekeeper.

His criticism in a recent speech of “well-educated lawyers patronising vulnerable victims of crime with inflexible platitudes” will be seen as an attack on the liberal elite to which he once belonged.

Mr Macdonald also stated that the principles of jury trial, the presumption of innocence, a right of appeal and full disclosure of the State’s case are “non-negotiable”.

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