Having tried the papers, I found the following -
Police Gazette 19th February 1773
STOLEN, on Tuesday Night, the 15th Instant, out of the Stables of Daniel Wilshin, of Headstone, near Pinner, in Middlesex, a Black Mare, fifteen Hands high, a small Star in her Forehead, a Speck in the near Eye, a switch Tail, some Hair of which is rubbed off, full aged, and has been hurt in her Bearing, by having a Foal. Whoever will give Information where the said Mare may be found to Daniel Wilshin, aforesaid, shall receive Two Guineas Reward; or if offered to be disposed of, stop Her and the Party, and give Notice to Sir John Fielding, and you shall receive the same Reward from the Owner.