This paper addresses the production and the perception of 'intrusive [h]' in French learners' L2 English (e.g. : I h ate pasta instead of I ate pasta). Based on the phonetic description of L1 and L2 English word-initial vowels, this paper provides three explanations and three teaching applications to deal with such phonologically illicit occurrences. First, the onsets of English words are phonetically analysed in three types of data: i) a text read by 8 native English speakers and 10 French learners of English, ii) spontaneous speech elicited from 25 French learners and iii) a perception test taken by 30 French-speaking students. The results suggest that a pause, some glottalisation or some aspiration are three processes that increase the time span between two vowels in a hiatus context. Second, three processes accounting for "intrusive h" are put forward. Third, some phonetic training is proposed.