Dictionary of the British English Spelling System - 3. The phoneme-grapheme correspondences of English, 1: Consonants - Open Book Publishers

3.1 The general picture: the regular spellings of English consonant phonemes This chapter can be summed up by saying that 13 of the 24 consonant phonemes of RP have highly regular spellings (though for two of these, /w, ŋ/, positional constraints have to be stated), while the other 11 have to be analysed according to position in the word. So, the 11 consonant phonemes/b d g h m n p r t θ ð/are regularly spelt <b d g h m n p r t th th> respectively; /w/ (which occurs only before vowel phonemes a

Dictionary of the British English Spelling System - 3. The phoneme-grapheme correspondences of English, 1: Consonants - Open Book Publishers