Horspath's proud unbeaten record in Cherwell League Division 1 stretching back more than 15 years and spanning 82 fixtures finally fell with an eight-wicket defeat at Dinton.
The club hadn't lost a game in the top flight since suffering a seven-wicket defeat at Buckingham Town on May 16, 2009.
The side were undefeated in the remaining 16 games that year to finish third behind Dinton and Buckingham, before invincible seasons with 18-match unbeaten runs followed in 2010 (champions), 2012 (runners-up to Great & Little Tew) and 2013 (champions).
This year Horspath were unbeaten following the first 12 fixtures (with seasons 2011 and 2014-23 spent in the Home Counties Premier League).
However, the run came to an abrupt halt on Saturday as the runaway leaders were bowled out for 133 after being put in to bat.
There were no signs of what was to follow as openers Jimmy Phillips (27) and Tom Coleman (26) shared an opening stand of 59.
But after they both fell on that score in successive overs to Zargham Ali and Faisal Ali respectively, Horspath collapsed in spectacular style with six wickets going down for 12 runs to leave the visitors 71-6.
Zargham (4-37) was the chief destroyer, and although Stephen Green and Jehan Mohammed dug in to make 20 apiece, the damage had been done and Qadeer Hussain (2-21) returned to take the last two wickets with successive deliveries.
Ten wickets had fallen for 74 runs, and left Horspath facing a monumental task to preserve the unbeaten run.
Asad Rafiq (2-36) continued his fine form with the ball to remove both openers, but by then Dinton had 60 on the board.
And there was to be no further joy for the visitors as Toby Suttliffe (54no) and Mark Ludlow (33no) shared an unbroken stand of 75 to see the hosts home at 135-2 off just 22.3 overs. Suttliffe's runs came off 55 balls, hitting five fours and three sixes.
With Horspath picking up just two points and second-placed Didcot beating Cropredy by seven wickets, the lead at the top has been cut to 38 points ahead of next Saturday's home game against Cropredy.
Horspath 2nd suffered a dramatic one-run defeat against second-placed Challow & Childrey in a low-scoring Division 2 encounter at the Recreation Ground.
An excellent display with the ball saw the hosts bowl Challow out for 128 after putting them in to bat.
Openers Ryan Gordon (32) and Patrick Bryan (28) put on 59, before Sam Leslie picked up a wicket in each of his first three overs to spark a collapse.
The young left-arm spinner claimed a fourth victim, and with off-spinner Joval Calix taking two wickets in three balls it was 79-7.
Skipper Ryan Hicks (3-16) then polished off the tail as Leslie finished with 4-27 from 16 overs, while Calix picked up 2-20 off 12 overs.
Horspath, reduced to 10 men at the break between innings due to illness, made a solid start in reply with Dominic O'Connor and Dan Todd putting on 39 for the first wicket.
But after the pair fell for 20 apiece to Joe Harris (5-31), the hosts slumped to 63-5.
Charlie Turner hit 31 to lift Horspath's hopes, but when he fell to Ross Packham (3-43), the home side were 106-8 with the last pair at the crease.
Hicks, accompanied by Leslie, inched the hosts towards the target with the captain making 26 before he was caught behind with his side agonisingly falling short of victory at 127 all out.
The side will bid to bounce back at Witney Swifts next Saturday.
Horspath 3rd crashed to a 171-run defeat at home to Westcott in Division 3A.
Oliver Murray hit an unbeaten 100 to steer the visitors to 241-8 dec after they chose to bat with Cade Linde making 32.
Off-spinner Luke Heritage (3-74) was Horspath's most successful bowler, while Sammy Parker took 2-43.
But the hosts were then skittled for 70 with only skipper Mohson Rana (26) providing any resistance as Alimar Khan (5-17) wreaked havoc.
The side, who drop to ninth place, are away to Great Brickhill 2nd next Saturday.
Adrian Manger's five-wicket haul couldn't save Horspath 4th from a 101-run defeat at second-placed Garsington in Division 5C.
The veteran seamer picked up 5-66 from 14.5 overs as the hosts were bowled out for 182 after being inserted.
Ben Wise (2-12) reduced Garsington to 4-2, before Umang Goel (40) and opener Sandeep Gummadelli (27) put on 66 for the third wicket.
Manger dismissed the pair and Horspath were on top as the home side slumped to 114-8.
However, Bhargav Satish (33) and Santosh Kumar Sahu (29) frustrated the visitors with 56 for the ninth wicket, before Manger completed his five-wicket haul to end the innings. Robin Pykett (2-43) provided good support, while Joe Garrow picked up a wicket on his debut.
Horspath, though, then slumped to 81 all out with extras top-scoring with 20 as Goel (5-12) proved the chief destroyer.
The side are at home to Wootton & Boars Hill on Saturday.