Heavyweight Anthony Joshua spectacularly knocked out Robert Helenius with one punch in round seven, after boxing tentatively in the first half of the fight at London's O2 Arena.

The 33-year-old Briton - who was jeered by fans during the fight - landed nothing of note until an overhand right ended Helenius' night.

The win - Joshua's first stoppage win in two and half years - sets up a blockbuster fight with American Deontay Wilder in January.

"It's a fickle sport, you've got to be real about this industry and not get caught up. I've done my job tonight," Joshua told BBC Radio 5 live.

When asked in the ring about the potential fight with Wilder, Joshua joked: "My back's gone, is there a doctor in here? I want to carry this heavyweight division to the top."

After the knockout, an emotionally charged and smiling Joshua climbed out of the ring, high-fived fans and shared a beer with Irish mixed martial arts star Conor McGregor.

Helenius needed oxygen after the heavy knockdown, but recovered and left the ring unassisted after congratulating Joshua.

Joshua extends his record to 26 wins - with 23 stoppages - and three defeats.

Finland's Helenius - who took the fight on a weeks' notice after Briton Dillian Whyte failed a voluntary drug test - loses his fifth pro fight in 36 outings.

From cautious start to vintage 'AJ' finish

Joshua struggled to find any rhythm but the manner of the finish may just be the confidence-boosting win he so desperately needed, and a gentle reminder to other heavyweights he is not yet done.

Helenius made his way to the ring in a packed out arena at the late time of 23:10 BST. Fans were offered a full refund when Whyte was withdrawn from the card but such is the draw of Joshua - there were no empty blue seats once the main event started.

The Briton confidently strode to the ring to a medley of a violinist playing the title song from the film 'The Godfather' and then the more upbeat 'Insomnia' by Faithless.

The 2012 Olympic gold medallist - fighting at the O2 Arena for the ninth time - kept his eyes firmly locked on Helenius during the introductions, who mockingly clapping back.

Helenius took the middle of the ring and swung a wild left in the first few seconds. The 'Nordic Nightmare' looked unfazed by the hostile atmosphere but neither man landed anything of note in a cagey opener.

Joshua was moving freely, looking to set traps but throwing single shots and not imposing himself on the stand-in fighter.

Fans started to become restless as early as the third. Boos echoed around the arena. The crowd wanted to see combinations, not this tentative approach.

Joshua had not knocked out an opponent in the first half of a fight since beating Eric Molina in 2016, a staggering statistic for someone once considered one of the heaviest hitters in boxing.

The Watford-born fighter landed a solid left in the fourth which sent Helenius backpedalling, but there was no sustained attack to follow.

Helenius grew in confidence, landing jabs to mark Joshua under the eye in the fifth. There were more jeers from a bored crowd at the halfway stage.

"It's hard to find the right hand," Joshua told trainer Derrick James. The American replied: "Keep trying."

Joshua adhered to the instructions. Those fans who left their seats missed what promoter Eddie Hearn described as the "knockout of the year".

A double feint followed by a right sent the Finn to the canvas, with referee Victor Loughlin halting the contest.

'We hope Wilder fight is imminent' - Hearn

Representatives from Saudi Arabia were in attendance, keen to conclude negotiations for a Joshua-Wilder mega-fight in the Middle East early next year.

All Joshua had to do was avoid a potential banana skin in Helenius. Fortunately for him and Wilder, there was no slip-up.

"We hope it's imminent," Hearn said. "That's why he wanted the Dillian Whyte fight, it's hard for him to get up to fights like this.

"If he hits Wilder on the chin then it's over. This is about Anthony Joshua now, it's not about pleasing others. He's given everything to British boxing."

Joshua-Wilder is a fight which has been mooted several times before, notably when the two heavyweights collectively held all four world titles.

Boxing politics starved it from happening then, but it appears the money offered for a Middle East showdown will be too good for either fighter - or their promoters - to turn down.

The winner will be propelled back towards world-title contention, the loser consoled by a career-high purse.

Alabama's Wilder is one of the most ferocious punchers in heavyweight history. 'The Bronze Bomber' stopped Helenius in under three minutes in October, and Joshua was under pressure to deliver an equally devastating, statement win.

Despite the sensational finish, there are still plenty of question marks surrounding Joshua's performance. The same cautious approach may not be wise against Wilder.

"I just want to see AJ fight someone of the calibre of Robert Helenius and treat him like Wilder," former world champion David Haye said on BBC 5 live.

"He can't just stand there and jab, it doesn't work against Wilder. He will run through him."

Credit: The BBC