What limits the size of a battleship?

Is there a practical upper limit to battleship size in this scenario?

Very large ships are technically possible, but the practical limit is set by how many ships the Royal Navy needs and can sustain across its commitments.

A battleship of around 120,000 tons is proposed as technically conceivable, without a worked design. The harder question is whether the Royal Navy could afford and sustain enough ships of that size. Its normal commitments from the 1920s onward are estimated here to require roughly 24 battleships available for service, including squadrons for home waters, the Mediterranean, and the East. Each increase in individual ship size must therefore justify its effect on fleet numbers. Operational coverage and support would impose a practical limit before a theoretical maximum displacement did.