The attorney general’s decision to block the publication of letters written by Prince Charles to government ministers was ‘unlawful’, the Court of Appeal ruled today.

Lord Dyson, head of the civil judiciary in England and Wales, led judgment in R oao Evans v Attorney General and R oao Evans & Information Commissioner v 7 Govt Depts (Princes Charles letters case).

In 2012 the attorney general Dominic Grieve blocked a decision by the Upper Tribunal Administrative Appeals Chamber to allow the letters to be disclosed under the Freedom of Information Act.

Disclosure of the correspondence ‘could damage the prince of Wales’ ability to perform his duties when he becomes king’, he said.

But Dyson ruled today that Grieve did not have reasonable grounds to quash the decision with a 53(2) certificate under the Freedom of Information Act. 

‘The mere fact that he reached a different conclusion from the [upper tribunal] in weighing the competing public interests involved was not enough,’ said Dyson. 

‘He had no good reason for overriding the meticulous decision of the UT reached after six days of hearing and argument. He could point to no error of law or fact in the UT’s judgment approved by the court,’ he said.

He also said the certificate is incompatible with EU law.

The attorney general’s office said in a statement: ‘We are disappointed by the decision in the Evans (Prince of Wales letters) case. To protect the principles at stake we will pursue an appeal.’

The Campaign for Freedom of Information, which had intervened as an interested party, welcomed the Court of Appeal’s ruling. 

Maurice Frankel, the campaign’s director, said: ‘The FOI Act has an elaborate appeal process, which the government could have used to challenge a decision it believed was wrong. Instead it has attempted to squash the decision, bypassing the need to argue its case, by use of a veto.

‘The court’s ruling will make it much harder for government to override a well-argued tribunal case in future. Disagreeing with the decision will not be enough, it will have to show why the decision is flawed or that circumstances have changed since it was reached. That is a major improvement to the public’s right to know.’