ALMA Large Programme observing strategy. Example observations of the targeted fields Q1431−0050 and Q0152+0023. Left panel: Broad-band HST/WFPC2 imaging displaying the exquisite spatial resolution afforded by space observations. The top row illustrates cases where they are distinct quasar absorbers at different redshifts with associated galaxies highlighted in blue and green. The purple star marks the position of the background quasar labeled “QSO” in the middle panel. Middle panel: VLT/MUSE white light of the same fields showing the position of the corresponding galaxies for which a spectrum is extracted. Right panel: ALMA observations of the same fields. The bottom row illustrates that in ALMA band 4, several overlapping pointings (shown as red circles) are used to cover all the galaxies associated with the absorbers and detected in HST and VLT/MUSE. The ALMA Large Programme observing strategy is thus optimised by targeting spectrally and spatially multiple VLT/MUSE-detected galaxies.