Why Britain was essential to naval treaty limits

Why would treaty powers make concessions to keep Britain inside the naval treaty system?

Britain's industrial and naval position meant that its absence could unravel limits for everyone else.

The answer treats British participation as a practical prerequisite for arms control rather than a courtesy to London. Britain was still a leading builder of battleships and other warships for foreign powers. If it remained outside the system, Japan would have little reason to accept limits. Japanese freedom to build would then push American construction and unravel the agreement across the major navies.