Leamington started the day in third place in Premier Division Two, needing to beat hosts Tamworth and hoping that one of Harborne and Ombersley, who occupied the promotion spots, slipped up.
As it was, leaders Harborne lost by three wickets to Oswestry, opening the door for Leamington who made no mistake courtesy of a crushing nine-wicket win.
Craig Miles picked up a wicket with his second ball after Tamworth opted to bat.
Things did not improve for the home side as Miles’ ten-over spell of five for 34 left them struggling on 64 for seven.
Miles’ impeccable spell was well supported by Joe Midgley (1-14) and Matthew Davison (2-22), with the tail mopped up by off-spinner Perry Derrick (2-22) as Tamworth were bundled out for 117.
In response, Leamington lost leading runscorer Harrison Smith for three which brought skipper Jonathan Wigley to the crease.
He steadied the ship, supporting the in-form Luke De Souza who hit 10 fours in a brilliant 64 not out.
Wigley finished on 47 not out as Leamington knocked off their target in the 25th over before an anxious wait on their promotion rivals delivered the news they were craving.
Leamington 2nds were crowned Warwickshire Division Two champions after beating Marston Green by 142 runs at Arlington Avenue.
After the hosts won the toss, Waqar Ahmed got the Spa men off to a brisk start until he snicked behind for 24.
Ibby Afzal soon followed him when Elliot Dunn-Ward cleaned him up first ball to leave Leamington on 45 for two.
This brought James Gilchriest to the crease and together with Jacob Sargeant he batted patiently for 27.
After Gilchriest fell for 27, Sargeant upped the tempo playing some graceful shots off his legs and through the covers.
Leamington were well poised at 178 for four when Billy Hallett walked to the crease and he let loose, dispatching the Marston Green bowlers to all parts of the ground for a quickfire 37 off 23 balls.
Jimmy Gethins (23 not out) joined the party as Leamington ended up on a season-high of 284 for six, with Sargeant carrying his bat for a faultless 135.
Chris Guy struck early on in the reply, bowling Oliver McMullen for a duck, while Jason Butler had Lee Davis caught smartly by Sargeant, also without scoring.
From that point on Marston Green were never in the contest.
Zaheer Suliman made 45 until Guy caught him magnificently on the boundary off the bowling of Nick Couzens, while skipper Richard Walker hit some lusty blows in his 35.
However, Couzens’ second wicket of the afternoon ended the innings on 142 to spark home celebrations.