The bomb was left in a holdall in Exchange Street West, where it exploded shortly before 7pm on Friday 13 December - with an estimated 1,000 people affected, according to police.A warning had been given, but the device was left in a different area and police were still clearing people from several premises when the bomb went off.On Thursday, two images were released of a man on a bicycle on Talbot Street and in At Anne's Square.Officers believe he is the man who planted the holdall.The attack ruined a night out for hundreds of people, but it had the potential to injure or kill.DI Chris Wilson, Serious Crime Branch"These images were taken at 5.46pm when the area was busy," Detective Inspector Chris Wilson, from Serious Crime Branch, said."In Talbot Street, the cyclist actually moves in the opposite direction to the traffic. In St Anne's Square, the holdall is visible beside the bike's handlebars."He added that police inquiries are progressing."We have established that a pressure cooker was used as part of the device," DI Wilson said."I am appealing to anyone who was in the Cathedral Quarter around 5.45pm and saw a man on a bike wearing a black hoody and carrying a black Slazenger holdall to contact the police."Anything you saw or heard may be of assistance. Or if you know anything about the attack or the cyclist, please contact us."Anyone with information is asked to contact detectives on 028 9180 1507, or information can be passed anonymously via Crimestoppers on 0800 555 111.