The climax of his boxing career was defined by three bouts with his former mentor and second Richard Humphries between 1787 and 1790.
 The first, and less known of these took place on 9 September 1787; Mendoza lost in 29 minutes.
 This fight was not considered as important by historians, perhaps because Humphries dominated, or because there were fewer persons in attendance.


The second bout with Humphries set history.
It was the first time spectators were charged an entry-payment to a sporting event.
 Mendoza and Humphries were personally involved in planning the entry price for attendees, and used newspapers to drum up interest with the intent of obtaining a more profitable deal.
The fights were hyped by a series of combative letters published between Humphries and Mendoza.
Their meeting finally took place, after postponement, on a rainy 9 January 1788 in Odiham, Hampshire and was attended by 10,000 spectators.
 
Included in the audience were the Prince of Wales and the Duke of York, who wagered 40,000 pounds on the match.
Humphries was a 2–1 favorite to win, though Mendoza had his own followers and was heavily backed by the Jewish community, who placed bets and comprised ten percent of the audience.
   
The fight was disrupted from a foul called when Humphries' second, the former champion, Tom Johnson blocked a blow but, according to Mendoza's account, this did not end the fight.
According to his own account, Mendoza slipped on the wet boards of the ring and badly sprained his ankle, preventing him from continuing, and requiring him to forfeit the bout.

At least seven English newspapers of the era, including London's Times and Chronicle, published articles on the Mendoza-Humphries bouts, and United States papers ran stories as well.
 In one newspaper article to advertise their meeting, Mendoza taunted, "Mr. Humphreys is afraid, he dares not meet me as a boxer … though he has the advantages of strength and age, though a teacher of the art, he meanly shrinks from a public trial of that skill".
 Humphries replied Mendoza should make the same claim in the ring, and vowed to meet him.

In his third bout against Humphries on 6 May 1789 in Stelton, Hastingdonshire, Mendoza dominated and won on a foul in the 65th round when Humphries was believed to have dropped to the ground without being hit.
 Mendoza had trained for the bout at the Essex home of his strongest backer, Sir Thomas A. Price.
After the win, Mendoza claimed the middleweight championship of England, and hoped to lay claims to the heavyweight championship as well.
 The specially built arena had tiered seating and could accommodate up to 3000 people, a more modest crowd than at his second bout.
 The battle commenced a  little after one o’clock in the afternoon.
The smaller crowd may have been due to Hanstingdonshire being a long journey for many fans, ninety miles from London.
It was clear early in the fight that Mendoza's hand and foot work were vastly superior to Humphries', though both men were accomplished scientific boxers and had studied each other's style.
 The Times of London declared Mendoza the champion of England.

Mendoza won his fourth and final bout with Humphries on 29 September 1790 in an incredible 72 rounds in Doncaster, successfully defending what he considered the Middleweight championship of England, though there was no unified body sanctioning the title at the time.
Recognized by many for his previous win, Mendoza was the 5–4 favorite, and he thoroughly thrashed his opponent, ten minutes into the bout.
 Pierce Egan, English boxing author of the period, noted that many in the crowd were behind Mendoza although many London fans were antisemitic, and that the "humanity of Mendoza was conspicuous throughout the fight—often was it witnessed that Dan threw his arm when he might have put in a most tremendous blow upon his exhausted adversary".
The climax of his boxing career was defined by three bouts with his former mentor and second Richard Humphries between 1787 and 1790.  The first, and less known of these took place on 9 September 1787; Mendoza lost in 29 minutes.  This fight was not considered as important by historians, perhaps because Humphries dominated, or because there were fewer persons in attendance.

The second bout with Humphries set history. It was the first time spectators were charged an entry-payment to a sporting event.  Mendoza and Humphries were personally involved in planning the entry price for attendees, and used newspapers to drum up interest with the intent of obtaining a more profitable deal. The fights were hyped by a series of combative letters published between Humphries and Mendoza. Their meeting finally took place, after postponement, on a rainy 9 January 1788 in Odiham, Hampshire and was attended by 10,000 spectators.  
Included in the audience were the Prince of Wales and the Duke of York, who wagered 40,000 pounds on the match. Humphries was a 2–1 favorite to win, though Mendoza had his own followers and was heavily backed by the Jewish community, who placed bets and comprised ten percent of the audience.    
The fight was disrupted from a foul called when Humphries' second, the former champion, Tom Johnson blocked a blow but, according to Mendoza's account, this did not end the fight. According to his own account, Mendoza slipped on the wet boards of the ring and badly sprained his ankle, preventing him from continuing, and requiring him to forfeit the bout.
At least seven English newspapers of the era, including London's Times and Chronicle, published articles on the Mendoza-Humphries bouts, and United States papers ran stories as well.  In one newspaper article to advertise their meeting, Mendoza taunted, "Mr. Humphreys is afraid, he dares not meet me as a boxer … though he has the advantages of strength and age, though a teacher of the art, he meanly shrinks from a public trial of that skill".  Humphries replied Mendoza should make the same claim in the ring, and vowed to meet him.
In his third bout against Humphries on 6 May 1789 in Stelton, Hastingdonshire, Mendoza dominated and won on a foul in the 65th round when Humphries was believed to have dropped to the ground without being hit.  Mendoza had trained for the bout at the Essex home of his strongest backer, Sir Thomas A. Price. After the win, Mendoza claimed the middleweight championship of England, and hoped to lay claims to the heavyweight championship as well.  The specially built arena had tiered seating and could accommodate up to 3000 people, a more modest crowd than at his second bout.  The battle commenced a  little after one o’clock in the afternoon. The smaller crowd may have been due to Hanstingdonshire being a long journey for many fans, ninety miles from London. It was clear early in the fight that Mendoza's hand and foot work were vastly superior to Humphries', though both men were accomplished scientific boxers and had studied each other's style.  The Times of London declared Mendoza the champion of England.
Mendoza won his fourth and final bout with Humphries on 29 September 1790 in an incredible 72 rounds in Doncaster, successfully defending what he considered the Middleweight championship of England, though there was no unified body sanctioning the title at the time. Recognized by many for his previous win, Mendoza was the 5–4 favorite, and he thoroughly thrashed his opponent, ten minutes into the bout.  Pierce Egan, English boxing author of the period, noted that many in the crowd were behind Mendoza although many London fans were antisemitic, and that the "humanity of Mendoza was conspicuous throughout the fight—often was it witnessed that Dan threw his arm when he might have put in a most tremendous blow upon his exhausted adversary".
Daniel Mendoza