The fire is started in a backroom. When the building is seen from the outside a moment later, the fire has several starting points on both floors all around the building.
A henchman of Mr G is instructed by phone to beat up Baxter. However Baxter is ready for him and knocks him out. The obvious thing to do at that point would be to hold the man for questioning about the gang; but he just disappears from the film and is never seen again.