How might a Lancaster hunt submarines?

How would a Lancaster carry out anti-submarine operations despite the concern about low-altitude flight?

The proposal uses radar to find surfaced submarines, then attacks them, with an added downward-firing cannon considered as a speculative adaptation.

The suggested patrol uses radar to find submarines on the surface, then descends enough to identify the target before attacking it. Concern about Lancaster's low-altitude handling prompts the alternative of firing down from greater height. A large cannon is imagined as capable of piercing the submarine's pressure hull. The initial idea of replacing a belly gun is corrected later: a ventral mounting would have to be added. Possible arrangements include a retractable mounting or a side-firing weapon used while circling, compared with an AC-130. These proposed adaptations remain speculative, with no historical Lancaster anti-submarine gun fit established.