Green’s Dictionary of Slang

(UK Und.) the member of a team of highway robbers who organises the plan.

1591		Greene Notable Discovery of Coosnage in Grosart (1881–3) X 37: The Art of Cony-catching. These are the eight lawes of villanie leading the high waie to infamie. In High Lawe. The Theefe is called a High lawier. He that setteth the Watch, a Scrippet. He that standeth to watch, an Oake He that is robd, the Martin When he yeeldeth, stouping.
1608		Dekker Belman of London G4: He that setteth the watch is a Scripper.