FreeBMD has only two events with that spelling. A search under Runag* shows the most frequent is Runagall, but many variants, generally in SE England. However they seem to come to an abrupt halt in 1950.
Spot check of Runagall in the GRO index for 1998-2002 inc. retrieves three births and four deaths, scattered from Leicester to South Dorset but none in Essex.