Earls of Sussex at Knockaloe were the figment of imagination - there were Radcliffes at Peel + Knockaloe in 17th C ergo they were there in 15th/16th, pity about absence of records la la la...!

Have a look at who was trustee of the Lancashire Radcliffes early will in Vic history then look at the bunch who accompanied the first Stanley to the Island in 1405 - one name stands out.

Yes there was an earlier Radcliffe abbot - some records might survive in records of mother house of Furness - many publically available (in 1860s) documents of that period were noted by Oswald in his Monumenta