In this expert opinion, UCL's Dr Marzena Nieroda (GBSH) and Prof Philip Treleaven (UCL Computer Science) explore why fragmented health data remains the core barrier to truly personalised care — and how AI, when designed to connect knowledge across silos rather than deepen them, can enable a more person-centred approach. Drawing on two new UCL research papers on the Open Health platform and AI prompting, the piece argues that personalisation is fundamentally an integration challenge — not a technology one.