One of the most colourful commissioners in the history of the New South Wales police, Norman Allen had a relatively minor role in the Bogle-Chandler case. Having returned to work from leave in mid-January 1963, he decided to take personal control of the case, a move which does not appear to have lasted long.

Allen was much more famously involved in the Glenfield siege in 1968. A man named Wally Mellish stole a car, and when police arrived at his house, Mellish fired shots at them. A siege developed, hampered by the fact that also in the house were a woman named Beryl Muddle and her baby daughter Lesley, supposedly being held hostage. Allen personally took over the negotiations, entering the house several times, and eventually being held hostage himself. At one stage Mellish pushed the barrel of a shotgun into Allen's mouth. Mellish made three demands, for Muddle and himself to be married by the Long Bay Gaol chaplain, for a new gun, and for a helicopter. Astonishingly two of these three wishes were granted, the line being drawn at a helicopter. With Mellish having married Muddle, Allen pursuaded Mellish to give himself up. Allen promised Mellish that no charges would be pressed against him, and it appears that he meant it. To compensate for the trouble he'd caused, Mellish volunteered to join the army and go to Vietnam; he was admitted to a mental hospital, then served a lengthy prison term. With the siege over, Muddle said that she'd never loved Mellish and wouldn't be seeing him again. The Reverend Clive Paton, who married them, said later that she did love Mellish, otherwise he would not have performed the service. As for Allen, he served for a couple more years as the Commissioner.