To confuse the issue a little, some ATCAs at Preston Centre were trained up in 1967 (ish) to do the "A" side. I know because I was one of them but didn't do the job for very long because I got an ATCO cadetship and was posted out. The dismissive attitude of the time that ATCAs "had no responsibility" certainly didn't apply here. We had to use our initiative at times even though we weren't supposed to! I am not sure whether this was an experiment which was later abandoned or it continued till PATCC closed.