The signed 4ft 4in x 3ft 10in (1.31 x 1.16m) oil on canvas, showing the stallion with his Arab groom and a dog, was reputedly commissioned by Henry Cecil (1754-1804), the first Marquess of Exeter.
Records indicate that Wootton, who was the prime bloodstock painter of his day for the landed gentry, made nine portraits of the horse, a common practice for such a famous subject. The first was finished in 1724 and one version was included in Wootton's studio sale in 1761.
Of the nine, three are still known but this was a previously unrecorded version and was consigned by a Worcestershire family, who had owned the painting for over 100 years.
Offered in original untouched condition, it was estimated at £30,000-50,000 but was contested by two bidders after £38,000.
The final price beat the house record for Halls which previously stood at £180,000 for a table by Pugin.
The buyer's premium was 17.5 per cent.
By Anna Brady