Portrait of a Man (Timothy Thomas?)

Inscribed at lower left in graphite: JTh[?]; at lower left edge in pen and black ink: Timothy Thomas. chaplain to Lord Oxford. drawn by Sir J. Thornhill; on piece of paper laid down below bottom edge of drawing in graphite: This Fizz, so well drawn, you may easily know / was done by a kt for one Tim with an O.; in decorative border at lower left left in pen and black ink: N.B. the verses, are Mathew Prior's, and his own hand writing.; beyond decorative border at upper right in graphite: 41.