long arm of the law

a little of something goes a long way

Only a small amount of something is usually required to produce a great effect.

a week is a long time in politics

In politics, much change can occur in a short space of time.

an arm and a leg

Usually used after the verb cost, but also often charge, pay, and spend: a very high price for an item or service; an exorbitant price

arm candy

An attractive, seemingly romantic companion who accompanies a person in public solely so that one or both of the individuals can gain attention, enhance social status, or create an impression of sexual appeal.

arm to the teeth

To equip thoroughly with weapons.

arm up

to supply, or be supplied with, arms (weapons)

as the day is long

Unceasingly; very; thoroughly; to a very high degree.

Chalk Farm

[Cockney slang]arm