This small qualitative study will involve 7-10 patients who are within one year of completing cancer treatment, as well as some parents. Participants will be recruited from one centre, the Cambridge Teenage and Young Adult cancer Principal Treatment Centre. The three phases will involve a) participants being interviewed individually and attending a focus group, b) patients receiving the prototype co-designed intervention, and c) participants being interviewed after the intervention to provide feedback to allow further refinement of the intervention. The intervention will be delivered by an Allied Health Professional in the setting that participants have chosen. It is likely to involve, at a minimum, education about fatigue and support with increasing activity. It will not include administration of any medication.