I realised at the time that arresting me was illegal

University lecturer Mick Napier, now 64, was detained during a protest in St Mary’s Street, just off the Royal Mile, in May 2008.

Several other protesters had unfurled a banner reading “End the Seige of Gaza” from the top of an open-topped tourist bus when the arrest took place.

Mr Napier had been driving in a car behind the bus and stepped out onto the pavement when it pulled over and the police were called. When asked by an officer for his details, he declined to provide them, and was arrested and handcuffed.

He later said the handcuffing had injured his wrists, a claim confirmed by his GP.

He was released without charge, and complained about his treatment to police complaints commissioner, Professor John McNeill, who yesterday ordered police to apologise.

Mr Napier said: “I made the point that I didn’t think this was in any way a police matter, and I knew legally that unless the officers think a crime is being committed, that they have no right to ask citizens for any information at all. I was delighted with the decision – I was over the moon.”

Mr Napier, who is chairman of the Scottish Palestine Solidarity Campaign, added: “I was in genuine shock. The handcuffs were, without warning, applied to my hands that were wrenched behind my back and I was in excruciating pain. This all happened as I stood quietly on the pavement beside the most peaceful demonstration you can possibly imagine.”

Prof McNeill said police were only entitled to arrest someone for not providing their details if officers have “reasonable grounds for suspecting that an offence is being or has been committed”, and should inform the person of their suspicion and the nature of the offence.

Instead, the officer had told Mr Napier that he was trying to find out what offence, if any, had been committed.

Prof NcNeill told police to apologise for the handcuffing, saying it should not have occurred. He rejected another claim that a letter Mr Napier had received from the Deputy Chief Constable contained factual inaccuracies.

Prof McNeill told the Evening News: “In this case Lothian and Borders got it wrong and I expect them to apologise.”

A police spokesman said: “Lothian and Borders Police have received the reports from the Police Complaints Commissioner for Scotland and welcome the content of them. We will now review the findings of the report and report back to the complainer and the Police Complaints Commissioner.”

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