Siward was abbot of Chertsey Abbey, a Benedictine abbey in Surrey before he was selected for the see of Rochester.[1] He was consecrated in 1058. He died in 1075.[2] His death was commemorated on 30 October, so he probably died on that date in 1075.[1] After the appointment of Lanfranc as Archbishop of Canterbury, the new archbishop found only four canons at Rochester under Siward's authority.[3]
Fryde, E. B.; Greenway, D. E.; Porter, S.; Roy, I. (1996). Handbook of British Chronology (Third revised ed.). Cambridge: Cambridge University Press. ISBN0-521-56350-X.