The past tense, affirmative forms of cael often take a soft mutation because of the effect of the particles mi or fe which were often put in front of verbs. mi/fe indicate that the verb which follows is an affirmative one, not a negative or a question. mi/fe cause a soft mutation. Although fe/mi are not as often used as they were, except in some dialects, the soft mutation usually still remains in the colloquial language. (mi is often used in north-west Wales, for example, and fe sometimes in some other parts of Wales)
- Fe gawson ni amser da - we had a good time
- Mi gawson ni amser da - we had a good time
Similarly, the past and future tenses of gwneud are also usually mutated in the colloquial language.