Barnsley sealed promotion to the Championship as two goals in the first 19 minutes set up their League One play-off final win over Millwall.

Ashley Fletcher slotted home after just 88 seconds, before Adam Hammill's 25-yard curling shot doubled the lead.

Both had scored for Barnsley in their Johnstone's Paint Trophy final win over Oxford at Wembley eight weeks earlier.

Mark Beevers fired in Millwall's reply from close range but Lloyd Isgrove's header secured Barnsley's victory.

The Tykes were bottom of League One in December but a superb run of form under interim boss Paul Heckingbottom saw them finish sixth in the table, and their two-year exile from the Championship was ended by wins over Walsall and Millwall in the play-offs.

• Barnsley's play-off final win as it happened

Lions pay for slow start

Millwall were forced into a late change before kick-off when centre-back Byron Webster was injured in the warm-up, with Tony Craig taking his place.

A mix-up in the Lions defence from a long ball allowed Fletcher to take advantage, as the on-loan Manchester United forward held off Carlos Edwards and fired across Jordan Archer into the bottom corner.

The south London side lacked composure and cohesion in the opening 25 minutes, and Barnsley capitalised again when Hammill cut in from the left and bent an exquisite shot into the top corner without being challenged.

Beevers' close-range finish reduced the deficit but the second half was a scrappy affair with few clear-cut chances, and Millwall could not recover from their poor start.

Millwall had been looking to secure an immediate return to the second tier but boss Neil Harris, in his first full season in charge, will have to pick up his squad for another promotion bid next season, having finished fourth in the table.

Tykes show composure

Barnsley looked comfortable on their second visit of the season to the national stadium, having suffered just one defeat since mid-March to reach the play-offs.

With Millwall increasingly playing the ball long in the second period, it was the Yorkshire side who made the crucial breakthrough, as goalkeeper Archer failed to collect Conor Hourihane's corner and Isgrove headed into an empty net.

The Tykes looked more likely to score a fourth in the closing stages, although Chris Taylor forced Barnsley goalkeeper Adam Davies into a late save.

With 13 victories in 21 games, winning the club's first cup final since 1912 and now winning promotion to the Championship, Heckingbottom has made a strong case to take charge on a more permanent basis.

The 38-year-old - part of the Barnsley squad promoted from the third tier in 2006 - built on work done by Lee Johnson, who left Oakwell for Bristol City in February.

Man of the match: Adam Hammill (Barnsley)

Providing a constant threat for Barnsley on the left touchline, his goal - a sublime long-range effort into the top corner - put the Reds in the driving seat in the first half.

After a successful spell at Barnsley early in his career, Hammill returned to Oakwell in November with the club struggling towards the foot of League One.

His form has been a key reason for their improvement in the second half of the campaign, and having scored in their Football League Trophy final win in April, Hammill found the net at Wembley again to help his side to promotion.