Selby suffered a 30-run defeat in a low-scoring division three game at Hovingham, whose Richie Brown totally dominated the match.
Not only was he the only batsman on either side to play a significant innings but he then produced a devastating bowling spell as he captured 8 for 26 in 17.2 overs.
Richard Laycock claimed 4 for 21 and Chris Young 4 for 42 for Selby as Hovingham struggled to a disappointing 98 all out, a total which owed much to Brown's 39.
Brown then produced his match-winning bowling performance and, with Jonty Rounthwaite capturing the other two wickets for 23 runs, Selby were reduced to a paltry 68 all out.
There's no stopping Hornsea, who boast a 33-point lead after their clinical eight-wicket win over bottom placed Osbaldwick II.
Ed Baldwin made 25 for Osso but they could only muster 72 as Richard Medforth captured 4 for 12 in ten overs, John Lewis 3 for 25 and Aussie Michael Johnston 2 for 2.
Malton and Old Malton closed the gap marginally when they had a more productive victory at Bolton Percy where the home side could only make 145 for 7 despite a good knock of 57 from Howard Hall and a supportive 26 from Peter Houseman.
Daniel Foxton took 5 for 34 for Malton who were then pointed towards the winning post by Greg Johnson 35, Chris Hudson 42 and Shane Bonser 31.
Heworth II maintained their promotion drive at Cawood thanks to Graham Hogben whose unbeaten 95 set up a five-wicket victory.
Team-mate Jonathan Simpson, who hit a big hundred a few weeks ago, showed that he can also turn in impressive performances with the ball when he captured 6 for 52. After tea Nigel Bartram turned in a lengthy spell which earned him 4 for 95 as Heworth ran out winners at 170 for 5.
Woodhouse Grange II had the better of a draw with a New Earswick side whose last pair were at the wicket when the game ended.
When Woodhouse batted first, Dave Langton made 37 and Lee Wild 29 as they made 143 for 9 despite good bowling spells from Andy Freeman who took 5 for 61 and former Garforth player Richard Atkin (4-28).
In Earswick's reply, James Routledge made 27, Mark Benson 33 and Craig Stimpson 27 but Peter Nolton kept hold of the reins with 4 for 64. Then 16-year-old Neil Barrett almost bowled his side to victory taking 3 for 8 as Earswick clung on.
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