Figures chap in charge can ring back with story (9)

I haven't cracked this one yet — but the brilliant team at Times for the Times have:

FIB (story), then IC (in charge) + CAN + O (ring) reversed [back]. Collins: Italian mathematician: popularized the decimal system in Europe. Another answer outside my comfort zone but I was able to construct the name from wordplay and vaguely remembered it coming up before, most recently in August last year as it turned out.