Amir Khan showed he is not slowing down with an astonishing 39-second win over Phil Lo Greco on Saturday.

In his first fight in nearly two years, Khan announced he is still in business with his quickest professional win in a welterweight contest that was scheduled for 12 rounds at the Echo Arena in Liverpool.

Khan, who afterward challenged English rival Kell Brook to face him, showed he is still a force at 31 and is not slowing down with age or the layoff.

Khan (32-4, 20 KOs) wanted to impress in his ring return, the English boxer's first performance in the UK for five years and the first live boxing event on the new ESPN+ subscription streaming service.

And he certainly did that, even if there was less than a minute's action.

What a contrast this was to Khan's last performance, when he was knocked cold by Saul "Canelo" Alvarez, after stepping up two weight divisions, in Las Vegas in May 2016.

In his first fight in two years, Amir Khan defeated Phil Lo Greco in 39 seconds. Oli Scarff/AFP/Getty Images

Since then, Khan recovered from an operation on his right hand and took part in the British survival reality television game show "I'm a Celebrity...Get Me Out of Here!" which averaged between 8 and 10 million viewers every day for two weeks in the UK.

Khan's blurring hand speed was evident as he floored Lo Greco (28-4, 15 KOs), 33, with a left hook followed by an overhand right.

The Canadian looked shocked by the Briton's speed and shook his head when he got to his feet.

When Khan resumed his attack with fast and furious punches, Lo Greco folded on the ropes and the fight was waved off.

It was as easy as many of Khan's early first-round wins as a professional, but Lo Greco went ten rounds with Shawn Porter five years ago.

Khan's demolition was also better than IBF world welterweight champion Errol Spence's third-round knockout win over Lo Greco in June 2015.

"Khan is back," Khan said afterward in the ring. "I wanted to prove a point. I trained for a 12-round fight. My hand coordination is very sharp. I saw I hurt him with the left hook and it was over. I'm back with a bang. At the moment, I'm a 147-[pound] fighter. My target is to win another world title."

Khan -- last world champion at light welterweight six years ago -- sees his future at welterweight, where the champions are Keith Thurman (WBC-WBA), Spence (IBF) and Jeff Horn (WBO), who fights Terence Crawford on June 9.

But he confronted former IBF world welterweight champion Brook in the ring after.

This was Khan's first in a three-fight deal with promoter Eddie Hearn, who also works with Brook.

Hearn tried to make the fight happen in 2016 and 2017, but Brook now operates at super welterweight.

"My future holds some big fights," Khan said. "I want to give the UK fans some big fights and sell out arenas and stadiums. We have many fighters around, I want to fight the top guys, I want to win another world title. This is where me and Eddie need to sit down with Kell's team.

"The weight is an issue with Kell [Brook]. I'm a 147-pound fighter. I will fight and beat Kell Brook and the world knows it. Kell Brook has been living off my name for a long time. I came and signed with Matchroom, I'm the one chasing Kell."

Outside of heavyweight fights featuring Anthony Joshua, Khan-Brook is perhaps the biggest fight in British boxing.

"All the fans want the fight. He can go in the jungle and chase stars, but when he gets in with me, he will be seeing stars," Brook said.

Hearn wants to make Khan-Brook for late 2018 at the Manchester Arena.

"This fight should have happened 12 months ago, two years ago. We have still got time," Hearn said.