[3][4] In December 2016, he fought undefeated Luis Ortiz (26-0) on the undercard of Anthony Joshua vs. Éric Molina, losing by seventh-round stoppage.
[5] He fought Lenroy Thomas in May 2017 for the vacant Commonwealth heavyweight title, losing a split decision over twelve rounds.
[7] Two fights later, Allen travelled to Paris to face undefeated Olympic gold medalist Tony Yoka (4-0), but was unsuccessful in a tenth-round technical knockout loss.
[8] The biggest win of Allen's career came in a third-round knockout of former WBA (Regular) champion Lucas Browne in April 2019.
[18] Allen lost to Johnny Fisher via split decision on 21 December 2024, at Kingdom Arena in Riyadh, Saudi Arabia as part of the undercard for the heavyweight world title rematch between Oleksandr Usyk and Tyson Fury.