Perry's highest break against Doherty was 67

Perry thrashed the Irishman 5-0 to book his place in the quarter-finals.

There was also a whitewashing in Wednesday's other evening match, with Jamie Cope beating fellow Englishman Robert Milkins 5-0.

Earlier, Ronnie O'Sullivan beat David Gray 5-2 in another all-English encounter and Australian Neil Robertson beat England's Andrew Norman 5-3.

Interview: Ronnie O'Sullivan

Perry did not practise in the two weeks prior to the tournament because his wife gave birth but said he was coming into form.

That performance was a shock and I'm very disappointed Ken Doherty

"I was shocked to get through the group stages because I played badly in my first two matches and got a bit lucky," said the Cambridge player, whose highest break against Doherty was 67.

"Since then I've gone from strength to strength and tonight was my most complete performance for a couple of seasons.

"I feel very relaxed because I know that if I get knocked out I've got a big smile waiting for me at home."

Docherty said he was "very disappointed" by such a comprehensive defeat.

"My whole career has been like this. I'll play well in one match and not in another," said the 1997 world champion. "That performance was a shock."

Qualifer Cope, who played seven matches just to reach the tournament proper, continued his run with an impressive victory over Milkins.

The 21-year-old, who made a 147 maximum break in the round-robin stages, is now in his first ranking event quarter-final.

"I'm playing better and better," he said.

I want to be like Billy the Kid. A lot of snooker players are too intense and serious Ronnie O'Sullivan

In the afternoon session, O'Sullivan began with a 136 break and followed up with a 51 to go 2-0 up.

Former UK champion Gray hit back but another century from O'Sullivan put him 3-1 up. The players traded frames before O'Sullivan wrapped up victory.

O'Sullivan said afterwards that he was enjoying snooker again and that he would continue to play an attacking game.

"I won't stop playing an aggressive game because for me, to be great at your sport, you need to be aggressive," he said.

"I want to be like Billy the Kid. A lot of snooker players are too intense and serious.

"I know how to play a defensive game, Ray Reardon has taught me that, but I don't intend on having many matches like that."

O'Sullivan will now play Robertson, who came from 2-1 down to end the hopes of qualifier Norman.

Robertson has reached the quarter-final stage in six ranking events but never been further.

However, the Australian said he would not let that become an issue.

"It doesn't bother me at all. I think it's a good sign if you keep getting to quarter-finals," he said.

"Eventually I think I'll start to break through. I've lost a few close ones, but it's definitely not a stumbling block."