Darlington extended their unbeaten sequence to six games and are now breathing down the necks of Redcar, whose lead at the top has been reduced to just a single point.
The target set by Normanby Hall posed few problems for the Feethams side who paced their reply and earned a comfortable eight-wickets victory.
Neil Pratt (45) and Mark Stainsby (47) laid the foundations and the good work was carried on by Yorkshire's Simon Guy with 32 not out and Mark Jobling (21 not out). The pair were still together when the winning runs were accumulated from 45.2 overs. When Normanby Hall batted first, they made a reasonable 160 in 38.5 overs.
Steve McNicholas added 51 with eight boundaries and Mohamed Zahid scored 31 before Rees Barker struck a six and six boundaries contributing 40.
Mark Stainsby, who bowled three consecutive wicket maidens finished with four wickets for just 19 runs in an economical 13 overs, five of which were maidens and Paul Raine returned 4-42 from the 11.5 overs he sent down.
Redcar and Hartlepool were engaged in a nail-biting finish to their game which was drawn. Required to score 161, Redcar were 145-9 at stumps. A double blow to their hopes came when both Martin Hood (33) and Graham Bowen (46) were run out.
Following their dismissals, Redcar were always up against it as Ashley Day conceded just 38 runs in 17 overs and took three wickets.
Batting first, Andy Carter and Steve Chapman gave the Pool innings a good send-off but it never gained momemtum and after 50 overs, a total of only 160-9 was achieved.
Middlesbrough are still struggling at the bottom and they have now lost three of their first six games after going down heavily to Marske. Their total of 73 which took no fewer than 30.5 overs to compile was by far the lowest of the day. Their batting demise was brought about by Tim Hood who in 15.5 overs, including five maidens, claimed seven wickets for a meagre 38 runs.
When Marske made first use of the wicket the runs flowed and 50 overs produced the healthy total of 210-9. Hood (30) and Raf Rashid (42) put together a productive partnership for the third wicket and afterwards, Richard Rennard contributed a useful 37 even though James Beaumont picked up four wickets for 55 runs from his 13-overs spell.
Guisborough and Darlington RA were involved in a high-scoring drawn match when just six runs and two wickets separated the pair at the end.
On his day, Darren Hickey can take any attack apart as the champions found to their cost when he crashed three sixes and 14 boundaries making 104. Gerard Hull's 41 and 31 from Maroof Khan propelled the RA total to 222-8.
Guisborough's early reply was uncertain but Saul Clifford stood firm for 34 and Johnny May recorded six boundaries in 39 before being run out.
Chris Murray made a similar score but in the final analysis it was down to David Towse and Graeme Wrightson to steer the home side to 216-8 from 47 overs.
Yet a third game ended with little between the sides. Bishop Auckland were within three runs of success and had as many wickets remaining at Thornaby, whose man-of-the-match was professional Hrishikesh Kanitkar.
His innings of 79 which included six boundaries was vital as Paul Timmens returned the excellent figures of 4-66 in 24 overs.
Bishop's target was 167 and when Richard Hawthorne found the boundary line six times scoring 43 and Darren Blenkiron struck seven fours making 48, it appeared that the opening pair had put their side on the road to victory.
Amul Mazundar, batting at number three, contributed 32 but Kanitkar came up trumps for Thornaby and his 11 overs yielded figures of 4-46 as Bishops ended on 164-7.
Blackhall, whose only success came when they defeated Guisborough, are still struggling at the wrong end of the table.
Jonathan Barnes was as economical as ever and amazingly conceded just 18 runs in 23 overs bowling 14 maidens as the Colliers struggled through 46.3 overs for just 101.
George Kay gave admirable support with 4-26 in ten overs and at one stage was on a hat-trick.
Although Northallerton lost a couple of early wickets to Ben Usher, they were never troubled and Jerry Hall recorded two sixes and seven boundaries carrying his bat for 60 as the visitors recorded an eight-wickets win - their first of the season.
Saltburn maintained their early-season challenge for honours defeating Richmondshire by six wickets.
John Boardman's 6-50 had Richmond back in the pavilion for only 134 and Paul Ramage then led the Seasiders home when he opened the innings and contributed 63 to a six-wickets victory.
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