Number eleven Rachel Slater hit the winning two to long-on to help Northern Diamonds beat reigning champions Southern Vipers by one run in a last-ball thriller chasing 241 at Headingley.

Diamonds were on the ropes at 216 for nine after 46.5 overs in reply to 240 for eight.

Visiting captain Georgia Adams impressed with 57 and a season’s best four for 26 with her off-spin. But they are not yet over the line in terms of the semi-finals.

Diamonds remain top and Vipers could slip out of the top two later on today.

Debutant left-arm spinner Rebecca Tyson impressed with three wickets, but she couldn’t quite defend nine runs off the last over with Katie Levick at the crease alongside Slater.

They shared 25, with Slater finishing 18 not out. Leg-spinner Levick’s 13 had been preceded by three wickets.

The Vipers innings was built around a measured 82-ball innings from Adams.

She was supported by a quartet of scores in the thirties from opener Ella McCaughan, Georgia Elwiss, Emily Windsor, and Naomi Dattani.

Having elected to bat, Vipers made steady progress. There was little aggression in the innings, more determination to get themselves into the game following back-to-back defeats.

This eleven may have lacked the experience of previous title-winning Vipers sides, but they still found a way to a competitive total.

A superb diving catch in the covers from Abi Glen helped Scotland seamer Slater remove Rhianna Southby before Levick bowled the other opener, McCaughan, for 30 - 50 for two in the 14th over.

Adams and Elwiss then steadied with a no frills partnership of 76 in 18 overs.

Adams hit all six of her boundaries through the off-side in a 74-ball fifty, cutting and driving nicely, whilst Elwiss added 31.

Both then fell as part of a loss of three wickets for 30 runs as the score slipped from 126 for two in the 32nd over to 156 for five after 38.

Adams was bowled trying to cut a ball too close to her, Elwiss was run out by a direct hit at the non-striker’s end from mid-off, and Abi Norgrove was run out having slipped trying to get up from playing a sweep to short fine leg.

A trio of Vipers were run out, including new loan signing Dattani in the final over.

Dattani, on loan from Lancashire Thunder, hoisted the only six of the innings off Phoebe Turner’s seam over midwicket.

On Sunday, Dattani played against Diamonds for Thunder and was bowled by Turner, who claimed six wickets in that Southport fixture. Today, Turner only struck once, with Levick leading the way.

After bowling McCaughan and Adams, she later broke a crucial 47-run stand for the sixth wicket between left-handed Dattani and the ever-resourceful Windsor, getting the latter stumped as the score fell to 203 for 6 in the 45th over.

Diamonds lost stand-in captain Lauren Winfield-Hill - Hollie Armitage is on England duty in Ireland - early in their chase as she miscued Adams to mid-on, leaving the score at five for one.

But they were boosted by a 91-run partnership between Marlow and Duckworth, who were both strong on the drive.

Duckworth posted her maiden regional fifty and Marlow only her second, off 71 and 81 balls respectively.

However, both fell quickly after reaching their milestones as Diamonds lost three wickets for 26 inside seven overs to set them back at 122 for four in the 32nd.

Duckworth and Sterre Kalis were trapped lbw sweeping at Adams before Marlow was bowled by the seam of Elwiss.

Australian overseas all-rounder Erin Burns added 31, but when she sliced Tyson to short third - 153 for five after 38 overs - it felt like a defining moment. Not so.

Tyson also bowled a scooping Phoebe Turner and had Abi Glen (24) caught at backward point.

Sandwiched in between, Adams bowled Katherine Fraser before Freya Davies cleaned up Sophia Turner with a slower ball.

Slater and Levick chipped away at the target before, with three balls left, the former crashed Tyson through cover for four. Then came the winning two to long-on.