Leon-Saval co-invented the photonic lantern and is the fibre-device engineer of the SAIL programme. His group designs, draws and characterises multicore fibres, mode-selective lanterns, OH-suppression fibre Bragg gratings and hexabundles, and increasingly applies the same devices outside astronomy — in telecommunications space-division multiplexing and in medical endoscopy and imaging through fibre. The unifying technical problem is coupling a spatially-incoherent, aberrated beam into single-mode circuitry without losing photons. Positioned against the established body of NV-ensemble quantum sensing work — DEER, nanoscale NMR and T1 relaxometry protocols operating at pT/sqrt(Hz) field sensitivity — photonic lanterns are directly applicable to quantum sensing readout: the same device that feeds a seeing-limited telescope beam into a single-mode spectrograph can feed fluorescence from a scattering biological sample into a single-mode quantum-limited detector, preserving the photon budget that a pT/sqrt(Hz) NV measurement depends on.