King Lear's half confused with three daughters, primarily (8)

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

Another clever lift and separate, and another hard work anagram. The fodder is half of LEar (for real this time), plus THREE plus D(aughters) with the setter generously including “primarily”. “The Unready”reigned from 978 to 1013 and again from 1014 until his death in 1016.