AtLAST -- A five fold increase in the number of identified Strongly Lensed Galaxies in the sub-millimetre and its consequences

Strong gravitational lensing is a powerful probe of cosmology, dark matter (DM), and high-redshift galaxy evolution, but current samples of strongly lensed galaxies (SLGs) remain far too small to exploit its full potential. $\mathit{\text{Herschel}}$'s submillimeter (submm) surveys demonstrated that submm selection provides the most efficient and least biased route to identifying high-redshift SLGs, yet produced only a few hundred systems over limited, heterogeneous fields. Achieving the thousands of SLGs required for precision cosmology and detailed studies of distant dusty star-forming galaxies demands a new, wide-area, homogeneous sub-mm survey. A facility like AtLAST, capable of extending $\mathit{\text{Herschel}}$-like methodologies to much larger areas, is uniquely positioned to deliver the order-of-magnitude increase in SLG numbers needed for transformative progress.