The rain gave way to hail and thunder before spring sunshine presaged the return of the snow as all four seasons enveloped north Derbyshire in one day. As metaphors go, it seemed a pretty fitting reflection of the decade that has sandwiched Paul Cook’s first title-winning season at Chesterfield and the National League title that was clinched with this 3-0 win over Boreham Wood.

Jamie Grimes, captain and centre-back, scored twice in front of 9,826 home fans, the biggest number at the SMH Group Stadium in its 14-year history and, in between, Liam Mandeville scored within 30 seconds of the second half kicking off as Cook’s team sealed the championship that has been theirs for the taking since winning 12 of their first 15 games. Twenty-one points clear of second-placed Barnet, who have six games to play, they are the first team in senior football to win their title this season.

Related: Chesterfield dream of more Cup glory under Cook and ‘King of North Sea’

Mr Blue Sky had rung out as the teams came out and blue-and-white balloons were still on the pitch at kick-off. Cameron Coxe, the Boreham Wood right-back, went to pick one up but mishandled and stamped down on thin air. Nothing was going to burst Chesterfield’s balloon on their big day.

After creeping ever closer to a return to League Two with three successive playoff finishes – first stage, semi-final, then final – the Spireites are back in the Football League, six years since their second successive relegation. So much has happened since Cook was first making his managerial name here, leading them to the League One playoffs in 2015 before he went on his travels to Portsmouth, Wigan and Ipswich, but for now the focus is on the future. “We’ve got our club back,” the supporters sang in the final stages.

In the 14 years since Chesterfield left Saltergate, their charismatic but crumbling old home, the club have now been through three promotions, three relegations and pitch-invading protests leading to a community trust taking over from their previous owner, Dave Allen. There have been seven permanent managers in between Cook’s reigns, Martin Allen drawing nine successive league games and James Rowe departing by mutual consent over a much-delayed sexual assault charge.

That led to the return of Cook two years ago and last week the Kirk brothers’ 75% ownership of the club edged forwards. They have already invested £2m and, with Ashley working at the club regularly and Phil worth a reported £500m, the backing is there. That it comes from a Chesterfield family does offer an almost quaint reassurance.

Attracting an average gate of around 7,700, higher than the League One playoff campaign, is testament to the entertainment on view. The pain of losing last year’s Wembley playoff final to Notts County on penalties is now supplanted by this triumph.

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It was fitting that Grimes, who started every game under Cook since February 2022 until being suspended after a red card against Solihull Moors on Boxing Day, should frame the scoring on this memorable day. The distance for his two goals amounted to no more than three yards, as he headed home Mandeville’s corner in the 28th minute from close range and touched the ball over the line after Armando Dobra, the most skilful player on view, dribbled in along the left touchline midway through the second half.

That was Chesterfield’s 100th league goal of the season, on a day when Will Grigg, their 25-goal leading scorer, was sidelined with a hamstring injury. Chesterfield were still on fire without him.

Dobra played for Cook at Ipswich and looks well equipped to cope back at the higher level. Tom Naylor, for some observers the most accomplished player below the EFL, was a crucial signing from Wigan last summer, while Michael Jacobs has proven quality. Harry Tyrer, loaned from Everton, has been a consistent figure in goal .

Grimes said: “We’ve worked so hard all year, the sacrifices the lads have made have been incredible. Paul Cook puts so much belief in you, you go out feeling 10 feet tall for every game. The club’s on its way up and I’m so proud to be part of it.

“We’ll enjoy this and with a good pre-season who knows how far we can go. We’ve made a lot of sacrifices so tonight’s going to be a good night.”