Lauren Winfield-Hill’s brilliant unbeaten run-a-ball 125 guided the Northern Diamonds into next Sunday’s Rachael Heyhoe Flint Trophy final at Lord’s at the expense of champions Southern Vipers, who could not defend 227 at Headingley and lost by four wickets.

England fringe opener Winfield-Hill steered a chase which had stumbled to 79 for four in this winner takes all final group game, gaining help from fellow wicketkeeper batter Bess Heath, who contributed 54 to a fifth-wicket partnership of 129. 

The Vipers, the back-to-back champions who posted 226 for nine, must now go into Wednesday’s semi-final Eliminator clash with South East Stars - likely to be at Beckenham - in order to keep alive their hopes of the ‘Threepeat’.

If they win, all three RHF Trophy finals will have been contested between the Diamonds and the Vipers, the latter winning the previous two. Having reached four regional finals in all, the Diamonds will now hope to secure their maiden trophy.

The Vipers, for whom Georgia Elwiss top-scored with 61 off 95, came into this fixture top of the table and only ahead of the Diamonds on net run-rate after five wins apiece and lost with seven overs to spare. 

They fell to 24 for two inside four overs after electing to bat. 

Lizzie Scott flattened Ella McCaughan’s leg-stump with a big in-swinger in the opening over before Linsey Smith trapped England’s Maia Bouchier lbw for nine.

But Elwiss and fellow Georgia, her captain Adams, calmly steadied with a 72 stand in 17 overs before Adams had a momentary lapse in concentration on 33 to open the door again at 96 for three in the 21st.

She handed leg-spinner Katie Levick the first of two wickets when she was stumped by Winfield-Hill. 

Elwiss reached her fifty off 77 balls shortly afterwards, though lost Paige Scholfield bowled by Levick - 121 for four in the 29th over.

And she was gone herself four overs later when bowled playing back to one which skidded through from off-spinner Emma Marlow. 

At 143 for five after 33, the Diamonds had reasserted the authority they had gained in the opening stages.

Captain Hollie Armitage then struck with her third ball as Chloe Hill chipped her leg-spin to mid-off, the first of three wickets to fall for 23 as Tara Norris was run out and Alice Monaghan caught behind off Armitage, who returned three for 37 from seven overs.

The latter two fell in as many deliveries, leaving Vipers 182 for eight in the 42nd.

But, just as happened at the start, the Diamonds failed to maintain pressure, as conceding 32 runs in wides suggests.

Emily Windsor accumulated an unbeaten 49, scoring the lion’s share of 44 added for the last two wickets with Charlotte Taylor and debutant leg-spinner Finty Trussler. 

Armitage had the former caught at mid-on in the final over.

But the Diamonds’ task of removing the venom would be far from straightforwards against a Vipers team to be reckoned with. And so it proved, as they stumbled to 79 for four inside 16 overs.

Smith miscued left-arm seamer Norris to mid-off early on before second-wicket pair Winfield-Hill and Armitage shared 44. 

Then came the loss of three wickets for 17, sparked by a cutting Armitage edging the off-spin of Adams behind. 

That was followed by two wickets in 19-year-old Trussler’s second over, the 16th. Sterre Kalis pulled a full toss out to deep midwicket before Leah Dobson was lbw.

But Winfield-Hill, who won the Hundred at Lord’s with Oval Invincibles earlier in the month, was not to be deterred. 

She reached her eighth fifty of the summer in all cricket off 56 balls and was particularly strong on the drive. 

With Heath’s help, they positively turned the game back in their favour in a defining 25-over alliance.

And by the time Winfield-Hill reached her fourth career professional century - her first this summer - off 105 balls, the game had been iced at 195 for four in the 36th over. 

After reaching her fifty off 61 balls, Heath fell to Adams with 19 required. But it was inconsequential, as was the run out of Leigh Kasperek. Winfield-Hill finished it with her only six over long-on off Norris.