Leading through David Graham's brilliant 13th-minute header and dominating in entertaining style, Peter Jackson's side had an automatic promotion slot for the taking as they were roared up the tunnel at the break.

That chance had been lost, and possibly for good, by the time boos rang out at the final whistle following Paul Hall's double which gave battling Chesterfield six points at Town's expense this season and mathematical safety in League I.

So dramatic was Town's demise that they failed to create a single effort on target in the second 45 minutes.

Even Andy Booth - a surprise inclusion on the bench and sent on for the final 18 minutes - couldn't poach or create a late leveller as 492 travelling fans went wild and almost 13,000 others slipped away into the moonlight.

It was a sickening blow for Town - rekindling the bitterness of that last-day defeat at Cheltenham a couple of years ago - and I can't remember Jackson looking quite so gutted since then as he did last night.

He acknowledged Town's chances of automatic promotion now rely on other clubs slipping up, while there's also concern about only a three-point advantage on seventh-placed Swansea - especially as all the leading contenders have better goal differences than the Galpharm side.

Town's three matches left are against sides in the bottom five but, if they fail to re-fit the wheels which fell off so disastrously against Wayne Allison and Co, they can forget about any easy ride into possible post-season competition.

Playing with width, pace and passion in the first half, Town seized control and looked well set for the two goals and three points needed to elbow Colchester out of second.

Graham had a handful of chances including the one he put away, which followed excellent build-up from the two Dannys, Adams and Schofield, while Chris Brandon also had a fierce drive saved and Gary Taylor-Fletcher saw keeper Barry Roche scramble to smother his goalbound shot.

The non-emergence of lively full-back Andy Holdsworth (groin injury) for the second half seemed to have a massive impact on Town, especially as replacement Tom Clarke quickly had to go off feeling ill.

Chesterfield's switch to a 4-4-2 formation also paid dividends for manager Roy McFarland, whose men exploited too much space between the over-committed midfield and over-stretched defence and grabbed themselves a comeback win.

Keeper Paul Rachubka had already made tremendous saves from Mark Allott and Jamie O'Hara when Hall equalised on 54 minutes.

O'Hara and Allison were involved in the build-up and when the former Town man crossed low into the six-yard box from the left, Hall got a lucky touch to control before forcing the ball over the line.

Thirteen minutes later and Town's nightmare got much worse.

With the defence looking in disarray and cover from midfield non-existent, Allott sent Hall past the offside trap and, from long range, he was able to curl the ball beyond Rachubka and into the unguarded net.

McFarland, who was right behind the shot, was leaping in the air and clenching his fists in celebration long before the ball crossed the line.

He knew what an important moment it was, because Town's fluency was nowhere to be seen at that stage despite the best efforts of skipper Jon Worthington and hard-working Gary Taylor-Fletcher.

Schofield and Chris Brandon disappeared from the major action in the second half while there were half chances for Booth, Schofield, Graham and Mark Hudson against his former club in the closing stages.

Graham's high volley into the Chesterfield fans, however, summed up Town's night and, having made a mess of this assignment, they face a big test to make sure they don't ruin the run-in with further sloppy goals conceded and points lost.

Peter Jackson, scanned promotion prospects through the wreckage of last night's defeat and admitted: "It's no longer in our hands."

Town could have gone second with a two-goal win but are now fourth, just three ahead of seventh place.

"We've had a few setbacks in our time but this was a major, major disappointment," said Jacko.

"Saturday is obviously a must-win game and, with three left, we have to hope other clubs slip up to stand a chance of taking second.

"It's not in our hands any more and we've thrown away a golden opportunity - that disappoints me more than anything."

Town were today assessing the groin injury which forced Andy Holdsworth off at half time.

Illness victims Tom Clarke and John McAliskey were also being checked while Andy Booth and Phil Senior will not be risked in tonight's Reserve game against Walsall at the Galpharm (7.00) after their surprise return as substitutes.

Pawel Abbott will play some part tonight.

"We played well in the first half and created chances, but we needed a second goal to settle some nerves," added Jacko.

"If we'd got a second goal I think we would have won, but the disruption of having to bring players off didn't help and you can imagine what the atmosphere was like in the dressing room. Everyone was bitterly disappointed."

The run-in:

Southend - April 22 Doncaster (H); April 29 Swansea (A); May 6 Bristol City (H).

Colchester - April 22 Bournemouth (A); April 29 Rotherham (H); May 6 Yeovil (A).

Brentford - April 22 Swindon (A); April 29 Hartlepool (H); May 6 Bournemouth (A).

Town - April 22 Walsall (A); April 29 Yeovil (H); May 6 Swindon (A).

Barnsley - April 22 Blackpool (A); April 29 Bradford (H); May 6 Walsall (A).

Forest - April 22 Hartlepool (A); April 29 Bournemouth (H); May 6 Bradford (A).

Swansea - April 22 Oldham (A); April 29 Southend (H); May 6 Chesterfield (A).

Oldham - April 22 Swansea (H); April 29 Doncaster (A); May 6 Scunthorpe (H).

Paul Rachubka Little he could do with either goal after making a fine save from Allott's drive at the start of the ill-fated second half. Rating: 6/10

Andy Holdsworth Had an excellent first half before going off suffering a groin injury. His energy and attacking flair were missed sadly by Town Rating: 6/10

Danny Adams Involved superbly in the build-up to Graham's goal and put in some thumping tackles to try and inspire the team Rating: 6/10

David Mirfin Not the good result with which he hoped to mark his 21st birthday as Town slumped badly in the second period Rating: 6/10

Nathan Clarke Handled Allison really well in the first half and stuck to his guns in the second, although Town got badly exposed Rating: 6/10

Danny Schofield Posed a massive threat first half but completely faded out of the game in the second. Made Graham's goal superbly Rating: 6/10

Jon Worthington Bags of effort on his last appearance of the regular season and he deserved better than a sickening defeat Rating: 7/10

Mark Hudson Did some bright things and showed plenty of enterprise first half, but found the going a lot tougher after the break Rating: 6/10

Chris Brandon Went through his party pieces first half and was a genuine threat. Had one cracking drive beaten out by Roche Rating: 6/10

David Graham Scored a fine seventh goal for the club in the 13th minute with a header and had other chances. Faded late on Rating: 6/10

Gary T-Fletcher Never stopped grafting despite Town's woes in the second half. His breaks in the first half were a real feature Rating: 7/10

Chesterfield

Roche; Bailey (O'Hare 41), Kovacs, Downes, Picken; Hall (Larkin 86), Niven, Allott, O'Hara, Hurst; Allison.

Subs not used: Davies, Smith, Beckwith.

Jon Worthington

NO-ONE showed more commitment over the 90 minutes than the skipper, who will now serve a ban for three games. He kept going even when the wheels fell off for Town 2nd half

Town didn't look the same in the second half and sorely missed the strong contribution of full-back Andy Holdsworth on the righthand side. He went off at the break suffering a groin injury and his replacement, Tom Clarke, quickly fell ill and had to come off himself. Skipper Jon Worthington ended up at No2 before his ban

Former star Lee Richardson today told distraught Town: "Don't be scared of the play-offs."

Chesterfield assistant Richardson, a member of Peter Jackson's Great Escape team eight years ago, helped plot the 2-1 Galpharm defeat which leaves Town vulnerable in the top six.

He insists, however, that all is not lost for Town despite missing the chance to go second and winning only two matches in nine before Saturday's trip to Walsall.

"It's the most open division I've ever been involved in and it's still wide open," said Richardson. "I hope Town get there automatically, but I just feel there's a little bit of pressure around which doesn't help.

"I hope the young players at the club can cope with that, realise how well they've done and how well they are doing. They've just got to amass as many points as they can and if they have to go in the play-offs then so be it.

"It's no shame, no disgrace, it's just football: competitive.

"Playing like the first 20 minutes against us they've got a great chance."

Paul Hall's double won it for Chesterfield after David Graham had given Town a first-half lead.

"If Town go to Walsall and win, everyone will be lifted again," added Richardson.

"That's the nature of football and I'd be really pleased for Peter if they could do it. What happened to him with the club before was an absolute disgrace, terrible, and what he's done since he came back with the staff and young players is brilliant.

"It's a progressive club with a lot going for it and that's what you've to focus on."