Don’t worry, the Department has your back! Yeah, right.
No Police Constable shall take proceedings at law or by indictment for an assault upon himself, unless he has previously obtained leave in writing from the Commissioners. The Superintendents will in each case inquire into the circumstances, and report their opinion upon it to the Commissioners. The Constables will understand that their interests and safety are best consulted by a check being thus given to unnecessary or vexatious prosecutions, while they will at all times be efficiently protected by every legal means, in cases that require prosecution.
Source: Metropolitan Police. Instructions Orders &c. &c.1836. London: W. Clowes & Sons.