The Bees had lost in their last nine play-off campaigns but when Toney's spot-kick gave them the lead after just 10 minutes, it always seemed likely that the club's curse would be lifted. The Championship top goalscorer with 32 kept his nerve to slot home from the penalty-spot after Swansea goalkeeper Freddie Woodman took out Bryan Mbeumo.
The excellent Emiliano Marcondes doubled Brentford's lead just 10 minutes later with a cool finish to complete a textbook counter-attacking move and give Swansea a mountain to climb.
It could have been even worse for Steve Cooper's side when Toney's audacious volley from 30 yards looked to have beaten Woodman only for the ball to strike the underside of the crossbar.
Andre Ayew squandered a gilt-edged chance to halve the deficit when he missed the target with a header from just yards out moments after the restart. And Swansea's day went from bad to worse as after a spell of pressure Jay Fulton was shown a straight red card for a clumsy and reckless challenge from behind on Mathias Jensen.
That completely killed Swansea's hopes as Brentford made history to ease their way into the Premier League and spark celebrations amongst their supporters, most of whom will see their club play in the top-flight for the first time in August.
Pontus Jansson of Brentford lifts the Sky Bet Championship Play Off Trophy following victory in the Sky Bet Championship Play-off Final between Brentford FC and Swansea City at Wembley Stadium on May 29, 2021 in London, England.
Image credit: Getty Images
TALKING POINT - Brentford turn on the style to claim their spot in the big-time
With over £170m at stake, Championship play-off finals are often tight, cagey affairs. Not this time. Just nine months after losing to Fulham at Wembley, Brentford returned to the scene of such heartbreak with a clear focus and produced one of their best performances of the season to overcome Swansea in style.
Year after year, the Bees have lost key players. Ahead of this season they had to deal with the departure of now-England international Ollie Watkins to Aston Villa. But thanks to their shrewdness in the transfer market, they have been able to consistently compete at the top end of the table. Toney has not just been an adequate replacement for Watkins, but arguably the signing of the season and the division's best player. It was the former Newcastle United forward who was once again the star here. He looks every inch a Premier League player and now has a real chance to make his name in the top division.
But it has been far from a one-man show throughout this memorable campaign in west London. Brentford have been the division's neutral's choice for some time now thanks to their stylish, entertaining style of football. They will undoubtedly be favourites to go straight back down, but under their clever boss Thomas Frank, they have every chance of surviving. With a new purpose-built stadium fully prepared for the top-flight, these are hugely exciting times for the club.
MAN OF THE MATCH - Ivan Toney (Brentford)
When Brentford were awarded a penalty, there was only ever going to be one outcome. Plenty of other players would have caved under the pressure but Toney looked ice cool and finished with supreme confidence. But there was much more to his game than just a moment of remarkable composure, as he linked up attacks, made intelligent runs to drag defenders out of position, and his aerial prowess meant he won virtually every ball in the air. A top level performance - and there were many in Brentford colours.
10' - GOAL! Brentford 1-0 Swansea (Ivan Toney, pen): No mistake from the Championship's top goalscorer who sticks the ball right in the corner to leave Woodman with no hope. Brentford are ahead!
20' - GOAL! Brentford 2-0 Swansea (Emiliano Marcondes): It's a long way back for Swansea now! The Bees sting the Swans on the counter-attack and now Cooper's men are in real trouble. There's a scramble inside the Brentford penalty area following a free-kick, Jensen's clearance picks out Mbeumo on the left and he rolls it Roerslev. He looks up and picks out Marcondes, who finishes with the side of the foot.
21' - Brentford hit the crossbar! Toney takes fire from 30 yards with a spectacular volley, Woodman is beaten, but the ball strikes the underside of the crossbar and somehow stays out!
47' - Swansea chance! Oh my, Ayew should score! The Brentford defence is sleeping as Roberts is afforded the space to deliver a teasing ball across the face of goal, but Ayew fails to capitalise, heading wide from point-blank range.
65' - Red card! Their day goes from bad to worse as Swansea's Fulton is shown a straight red for a clumsy and reckless challenge from behind on Jensen. After a spell of pressure, the midfielder committed the foul in an attempt to retrieve possession just outside the Brentford penalty area.
Next season will see Brentford play top-flight football for the first time since the 1946-47 campaign; their 73 seasons since is the most different seasons played in between English top-flight campaigns.
Brentford will be the 50th different team to play in the Premier League, and the 10th side from London to do so.