I think I heard of that. Anglo-Saxon noblemen who served as Varangians, their own land haven fallen to harsh Norman rule, were settled there. Their Crimean colony, a little enclave on a peninsula which was then mainly Gothic and Pontic Greek (Pontic Greeks remained there until this minority suffered expulsion by Stalin after WW2 and final replacement by Russian settlers, already arriving there since Russian annexation of the Crimean Khanate in 1783), seems to have provided a source of recruits. The Swedish-Slavic Rus were an earlier source of recruits, but also a potential foe, while the Anglo-Saxons no longer had a home.