But information was not immediately passed on to investigating officers who spent months combing mobile phone records in the hunt for the Real IRA bombers, ex-police complaints head Nuala O’Loan added.

The perpetrators are believed to have used phones to communicate on their way to Omagh with the device.

Dame Nuala gave evidence to a committee of MPs at Westminster.

“I am satisfied that material was passed to Special Branch,” she said.

She talked about the reaction of secret service monitors.

“It triggered, and I am speculating, that the security services would be alarmed and distressed by the explosion and would immediately decide to search to see if they had anything which would be relevant, anything that had come in in the past hour or so.”

Ms O’Loan told the Northern Ireland Affairs Committee investigation opportunities could have been availed of.

She said there was a five-month delay in some cases as detectives combed through all the phone records in the area.