Why were the emergency services so slow responding to the Manchester bombing?

Claire Booth was put in the impossible position of having to decide whether to care for her sister or her daughter after the Manchester Arena attack. She understandably chose to look after her 12-year-old daughter, Hollie, but the decision still haunts her. More than anything, she wishes that emergency help had arrived quickly, in whatever form, and that the three of them had been taken to hospital for proper care. Kelly Brewster, her bubbly, music-loving sister did not survive the bombing. The speed of the emergency response may not have made a difference to Kelly but it may be that two others among the 22 victims could have been saved