This is the battered face of American John Heenan, the “Benicia Boy” – after slugging it out for 37 rounds with legendary Brighton prize-fighter Tom Sayers.

Now the unusual portrait, painted in the aftermath of what is generally considered the last great bare-knuckle fight, has surfaced at a London auction.

The unframed oil painting is inscribed across the bottom: “Yankee Gentleman as ‘painted’ by Tom Sayers.”

The 11in by 9in portrait, consigned by a private source, is estimated to fetch a modest £2,000 to £3,000 at Bonhams in London on October 29.

Standing 5ft 8in and weighing a modest 11 stone, Sayers usually fought men weighing at least three stone more than him but won the world title in 1851 when he defeated William Perry, “The Tipton Slasher”.

But he is best remembered as the first English boxer to fight an international match when he fought the taller and heavier Heenan at Farnborough, Hampshire, on April 17, 1860. It was in the seventh round that Sayers inflicted the damage shown in the portrait. According to a report: “Tom countered him heavily on the right cheek, drawing the claret ... which had the effect of closing his dexter goggle [right eye].”

After two hours and 20 minutes, Heenan’s corner jumped in to stop the fight. Lord Redesdale in his “Memories”, said: “... five more minutes would have given Tom Sayers a glorious victory”.

A draw was declared but Sayers was later acclaimed as the “World Boxing Champion”.

After the “Brighton Boy” retired from the ring he ran off the rails and died aged 39, from diabetes and tuberculosis, just five years after the Heenan fight.

Such was his popularity that 10,000 people attended his funeral in North London. In 1954 Sayers, who was defeated only once in 20 gruelling fights, was elected into the Boxing Hall of Fame.