Table 2 Qualitative data purposes and time points

Participant’s 1st

To explore:

Post consent and pre

interview

• Expectations of the CHESS intervention

randomisation

• Experiences of living with chronic headaches

• Trial experiences

Participant’s

To explore:

Post 4 months questionnaire

2nd interview

• Reflection on trial experiences

• Current headache experiences

• Use of the trial materials

• Early impact

Participant’s

To explore:

Post 12 months questionnaire

3rd interview

• Further reflection on trial experiences

• Current headache experiences

• Use of the trial materials

• Early impact

Intervention staff

To understand their experiences of delivering the intervention

End of all trial intervention delivery

GP feedback

To understand their trial experiences

End of practice patient’s involvement