Arsenal 4-1 West Bromwich Albion

Theo Walcott had scored three Arsenal goals all season before his hat-trick against West Brom

• Walcott scores third Arsenal hat-trick

• Forward makes first Gunners start since 14 March

• Arsenal ensure third place in Premier League

• West Brom's five-game unbeaten run ends

Theo Walcott scored a first-half hat-trick as FA Cup finalists Arsenal made certain of a Champions League group stage place by demolishing West Brom.

Walcott, making his first club start for more than two months, fired an early shot into the top corner, before poking in a second from close range.

Jack Wilshere thumped in a third from 20 yards, and Walcott tapped in a fourth before half-time.

Gareth McAuley headed a second-half goal for Albion.

Walcott is starting to regain his best form after almost a year out with a knee injury, while Wilshere has only recently returned to action after being plagued by ankle problems.

Both made a point, after scoring, of going over to the bench to celebrate with Arsenal physio Declan Lynch, who has done much to help them get back to fitness - but who is about to leave for a new role at Premiership rugby union side Bath.

Manager Arsene Wenger will be pleased that both players look ready to play a part in next Saturday's FA Cup final against Aston Villa.

And he will also be happy that his side have found their goalscoring touch after three successive home games without finding the net.

Arsenal needed a point to be certain of securing third place in the Premier League, while ensuring they avoided a Champions League play-off in August, and set about the task of winning the game with vigour.

Walcott struck early, thumping an unstoppable shot across keeper Boaz Myhill.

The forward then side-stepped Jonas Olsson to prod in a second from eight yards after Wilshere and Mesut Ozil combined to set him up.

His England colleague Wilshere struck a spectacular third with only 17 minutes gone, finding the top corner as Albion struggled to clear a set-piece.

Walcott, though, made sure of headline status by completing his hat-trick, tapping in after Santi Cazorla rolled the ball across the goal.

McAuley's consolation goal, his first in the league since December 2013, was headed in from a corner, with Arsenal keeper David Ospina at fault.

Arsenal eased off with victory secure, yet still could have had further goals, with substitute Aaron Ramsey striking the post before having a chip turned on to the bar by Myhill.

But they showed enough to strengthen their position as favourites to win the FA Cup next Saturday.

Arsenal manager Arsene Wenger: "Theo had a great game today. He was on fire and moved well. Jack Wilshere as well. I have not thought about a side for next Saturday. I wanted to pick a team to win this game.

"We had a slow start to the season, but progressively, we got stronger, and from January onwards we got competitive.

"We have qualified directly for next season's Champions League, but we want more. We want to challenge for the Premier League. But first we want to win the FA Cup next weekend."

West Brom head coach Tony Pulis: "We looked like a team who have played against Liverpool, Manchester United and Chelsea in the last few weeks. We've had a tough run-in.

"I think the performance against Chelsea took a lot out of the players. Maybe I should have rested a couple, because they looked jaded.

"It was a disappointment because we'd done so well. We hadn't reached the standards you need. But we were better in the second half."

Relive Arsenal v West Brom minute by minute

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Theo Walcott was called into the starting line-up in place of Olivier Giroud

Jack Wilshere's goal was his first for Arsenal since September

Wilshere did not play between November and May because of ankle problems

Walcott's hat-trick was his first for Arsenal since December 2012