Definition of "lett"

We grete you well. Wheras the Erle of Murray, and uther Noblemen and Gentlemen of Scotland, came into this our realme, upon our request, and by our saife conduct for their entry and departure, we lett you know, that we have licensed him, and them all, with their traynes, to returne into Scotland, there to continue in their former estates.

1754, Walter Goodall, “An Examination of the Letters, Said to be written by Mary Queen of Scots, to James Earl of Bothwell: Also An Inquiry into the Murder of Kind Henry. Vol. II”, in The Quenes Majesty to the Lord Wardens of the marches, for assistance of the Erle of Murray, Edinburgh, page 323