This paper reports on a study that seeks new insight into how the expertise of specialist mathematics intervention teachers might be harnessed to support classroom teachers to assist students who experience difficulty learning mathematics. Findings show that the classroom teachers' confidence increased after engaging in co-teaching cycles led by the specialists. The most highly ranked helpful actions of the specialist intervention teachers were 'suggesting appropriate tasks for a given topic,' 'team teaching with me,' and 'suggestions about content for the next lesson.' The findings suggest that teachers' professional learning needs vary and require a personalised response.