Mrs. Bargrave is the person to whom Mrs. Veal appeared after her death; she is my intimate friend, and I can avouch for her reputation for these fifteen or sixteen years, on my own knowledge; and I can confirm the good character she had from her youth to the time of my acquaintance.

This he avouches in the same breath in which he gives that "nature" to a participle and its adverb!

For Sir Launcelot always avouched with his knightly word, unto the last day of his life, that the Lady Guinevere was noble and worthy in all ways, wherefore I choose to believe his knightly word and to hold that what he said was true.