London & The South landed a huge blow in the Racing League title race on a night of twists and turns at Windsor on Thursday.
In a round that saw five of the competition's seven teams taste victory, the championship lead changed hands twice as Wales & The West tried their best to outdo their rivals.
With just a single point separating the top two at the start of the evening, Neil Callan had briefly fired his Wales & The West side in front with victory on Safari Dream.
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There were doubles on the night for The North and The East, while Ireland enjoyed a rare success courtesy of Jessica Harrington's raider That's Just Dandy.
But, the crucial clash came in the penultimate contest as leading rider Sean Levey led home a 1-2 for London & The South, helping Matt Chapman's side to a 48-point advantage as the competition heads into round five at Southwell on September 8, all live on Sky Sports Racing.
How round four unfolded…
With all eyes on the title tussle, it was The North who snuck under the radar in the opening race of the night as Vintage Clarets (12/1) got the better of London & The South's 5/2 favourite Equality.
In a typically feisty five-furlong sprint, Vintage Claret's rider Connor Beasley and Margo Ghiani on Equality were able to steer clear of the trouble in behind as they finished clear of Glamorous Breeze for Wales & The West, who was relegated to fourth after a stewards' enquiry.
That result briefly extended the lead for Matt Chapman's side but Wales & The West struck back immediately as 15/8 favourite Safari Dream scored in good style under Neil Callan.
Rod Millman's juvenile had himself been disqualified at Sandown last month but gave the judge no reason to intervene this time, beating Michaela's Boy and Gemcutter as The North picked up more vital points in second and third.
Callan told Sky Sports Racing: "When I got him I thought: 'Wow, he doesn't feel like a five-furlong sprinter! What he's doing now really bodes well.
"From two furlongs out I always felt he was going to win and he was gritty. He will get another furlong no problem and has a bright future."
Lir Speciale ensured success for back-to-back favourites as the 11/4 shot scored for The East in race three.
Roger Varian's three-year-old, making his first start since May, was kept in a good position throughout by Ray Dawson and galloped away to beat Scotland's Sound Of Iona, The North's Seven Brothers and fellow East runner Aramis Grey in fourth.
Dawson told Sky Sports Racing: "Fair play to Roger, he's got this horse back winning. It's nice to see him back after the wind op and performing because we've thought a lot of him.
"He's still very inexperienced but he's got a great mind."
The East fired in a quick double as 11/1 shot Croupier held off the late challenge of New Pursuit (London & The South) in race four.
Luke Morris came from last to first on Simon and Ed Crisford's three-year-old, with The North again in the places with Ana Gold and Ireland's Dairerin an unlucky fourth after coming wide through traffic.
Ed Crisford told Sky Sports Racing: "It's great to get 25 points on the board for the team and claw some back!
"He stumbled coming out of the gates but lucky there was plenty of pace on and he's done well."
Ireland have had a miserable time of things in this year's competition but got a morale-boosting victory as the Jessica Harrington-trained That's Just Dandy scored under Dylan Browne McMonagle.
The 9/4 shot showed plenty of heart to battle past London & The South's 15/8 favourite Majestic, with Alablaq for Wales & The West in third.
Just four points separated the top two going into the penultimate race of the evening, but London & The South stretched clear with a 1-2 as Sanitiser (15/2) led home team-mate Danville.
Sean Levey has made no secret of his desire to lift the jockeys title and the £20,000 bonus and the leading rider produced another well-timed attack to score over the 10 furlongs to extend his side's advantage to 37.
On his title ambitions, Levey told Sky Sports Racing: "This competition is all about points, whether that's winning, second or third.
"I'm excited and enjoying it. The atmosphere in the weighing room has been great and it feels like you're riding at a festival every time you come down here."
Round four ended as it began, with a victory for The North.
Young jockey Harrison Shaw produced a stunning front-running display on Richard Fahey's Wootton'sun (9/1) to bravely hold off The East's pair Haunted Dream and Eklil, while London & The South picked up valuable scores from fourth and fifth with Andaleep and Silverscape.