The note in my diary dated April 1 2002 quotes a security source describing the robbery at Castlereagh Special Branch offices as “an act of war”.

Two weeks after the break-in the intelligence assessment had become definite – what happened in that police building on St Patrick’s night was the work of the IRA.

That assessment has not changed. “PIRA did it,” a source told me yesterday. “We know who did Castlereagh – how they did it.”

They also know how the IRA covered its tracks – destroying a number of mobile phones used on the night of the robbery by chopping them into pieces and dumping them down a drain in west Belfast.

Information taken from room 220 in the police complex was moved across the border.

It contained many secrets, including the codenames of Special Branch agents. The IRA’s director of intelligence masterminded the Castlereagh operation.

This was the most embarrassing security breach in the history of the conflict – the IRA had been able to walk the corridors of Castlereagh and get inside the door of the “source handling unit”.

“If you are an SB tout you ring into 220,” a detective told me the day after the story of Castlereagh broke. He was explaining the significance of the office.

Now, republicans had a list of Special Branch officers and their telephone numbers and had also taken the log of “addresses of interest” – addresses of interest to the Special Branch right across Belfast.

The IRA denied it then and will deny it now.

A month after the robbery a senior IRA source told me: “The IRA did not carry out Castlereagh. Some section of British Intelligence did carry it out.”

I asked a senior police source if there was any change to the assessment of IRA involvement. “No, no, no – definitely not,” he said.

He is convinced the IRA did it – and quietly when no one is listening some republicans will tell you the IRA did it.

We may be at the end of the Castlereagh story – no one in court and the IRA saying nothing, admitting nothing.