For Sergeant RAPC, EPC was a must. My boss argued that the moment I got my second, there was a (theoretical) risk of Acting Sergeant at any time.
There was much tutting when I rocked up for EPC as a Lance Jack. As it happened I was promoted halfway through the course.
Also as it happened, of the four subjects (thinks) Military Calculations (sums), Army in the Contemporary World, Military Writing (or something, basic English) and one other, lost after 37 years), I was completely exempt ACW "because I had Linguist German" (me neither) and because I had A Level Maths I basically turned up for the exam. I'd done the 3 hour exam, checked my answers, rewritten without crossings out and walked out after ½ hour. There may have been wistful looks from ¾ of the course.