A senior MI5 officer has told the Manchester Arena inquiry that the intelligence agency downgraded what turned out to be “highly relevant” evidence about the suicide bomber Salman Abedi. Speaking from behind wooden screens, the officer, named only as Witness J, said there were two pieces of intelligence received by MI5 about Abedi in the months before the attack that were assessed at the time to relate to possibly non-nefarious or non-terrorist criminality. Only after Abedi detonated the bomb that killed himself and 22 concertgoers did MI5 realise the evidence was important. “Looking back, you can see it was intelligence that was highly relevant to the planned attack,” Witness J told the public inquiry into the atrocity on Monday. Giving evidence inside a bespoke wooden box to protect his anonymity, the officer offered to share the evidence with the inquiry only in a closed session, away from reporters and victims’ families. The inquiry heard that MI5 first received information about Abedi on 30 December 2010, the day before his 16th birthday, but there was “nothing to suggest” then that he was a risk to national security. From December 2013 to January 2017, he was in direct contact with three men, all separate “subjects of interest” – one suspected of planning travel to Syria, one with links to al-Qaida, and the third with links to extremists in Libya. And between April 2016 and April 2017, a month before the attack, he had contact with three more subjects of interest, all with suspected links to the Islamic State terror group. Intelligence on Abedi came in right up to the months before he blew himself up with a homemade bomb packed with shrapnel in the foyer of Manchester Arena at the end of an Ariana Grande concert on 22 May 2017. On one occasion Abedi had himself been made a “subject of interest”, but his file was closed five months later, in July 2014, based on a “lack of engagement” with extremists. Witness J was asked about two prison visits by Abedi to convicted terrorist Abdalraouf Abdallah, the second of which was in January 2017, shortly before he began planning his terror attack. He said there was no intelligence that the visit was related to attack planning: “There was no intelligence to indicate that the contact was related to Salman Abedi posing a threat to national security. The decision to not open [an investigation] was a reasonable one.” The inquiry heard that Abedi’s name also hit a “priority indicator” during a separate “data-washing exercise” as falling within a small number of former subjects of interest who merited further consideration. A meeting to consider the results was scheduled for 31 May 2017, nine days after the bombing. The investigation into the attack continues. On Friday a man was arrested at Manchester airport after he arrived back in the UK. He was held on suspicion of engaging in the preparation of acts of terrorism or assisting others to prepare, and was bailed pending further inquiries. Police have not named him, but he was from Fallowfield, the area of south Manchester where Abedi grew up.