The digraph ff at the beginning of a word is an anomalous feature, in lower case, of a few proper names in English. In that setting it has no phonetic difference from F, and has been explained as a misunderstanding of palaeography. In other words, ff, which is "Latin small ligature ff ", a stylistic ligature from Unicode, available now in some Latin script fonts, represented in certain traditional handwriting styles the upper case F.
In Spanish orthography, on the other hand, word-initial ff had a phonetic meaning, over a period of some centuries.