I wonder if someone could help me with a minor mutation query. In a book I am currently reading (‘Ar Daith Olaf’, by Alun Davies, quite a good read) there occurs at one point the phrase ‘Cam wrth gam’ (step by step), in the sentence ‘Cam wrth gam, troedfedd wrth droedfedd, rydyn ni’n dringo’r llwybr serth’. So, no mutation of the first ‘cam’, which is as I would expect. But in another place, we get the same phrase this time with the first ‘cam’ mutated: ‘Er gwaetha’r gwynt a’r glaw mae’r chwys yn diferu i lawr fy nghefn wrth i mi lusgo Alaw, gam wrth gam, i fyny’r llwybr’.
Is there an actual mutation rule at work here, or is mutation of the first ‘cam’ in the phrase simply optional and dependent on whatever seems to the writer to flow better, which may be influenced by nothing more than the phrase’s position in the sentence?
Thanks in advance for any enlightenment
