Davis, in his 26th season as a professional, led the 21-year-old 4-2 but was eventually beaten 5-4.

The six-times world champion missed a vital shot in the seventh frame which Murphy won on the black before sealing victory with breaks of 72 and 64.

"I had him on the hook and let him get away. I got punished for not finishing him off," said 46-year-old Davis.

"After that, he didn't miss a ball and I didn't get another chance.

"He started off like a racehorse, turned into a carthorse and then became a racehorse again."

Murphy said coaching from Joe Johnson had given his game a boost.

"This is one of the greatest days in my snooker career. I'm ecstatic," he said.

"But I'm here to win the tournament and the work I've done with Joe has given me tons of self belief."

Murphy faces world number four John Higgins or Harrow's Alfie Burden for a place in the quarter-finals.

Holder Chris Small had to come from 4-1 down to beat Stuart Pettman 5-4 in a marathon encounter.

The Scotsman was also 49-8 down in the deciding frame before calling on all his reserves of tenacity to clear up with 68 to the pink.

"I thought I was a goner in that last frame," said Small, who will meet either Stuart Bingham or Paul Hunter in the next round.

"I feel like I have just run a marathon. At 4-1 down I thought I was on my way home.

"But I just told myself to try and put some pressure on. I could see Stuart was struggling to get over the line and in the end I made one of the best breaks of my career to win the match."

Jimmy White made a successful start to the new campaign by reaching the last 16.

White, the world number 15, compiled breaks of 90 and 100 as he beat Northern Irishman Patrick Wallace 5-3.

"A win is a win so I'm pleased to get through. I scored well before it went a bit scrappy," said White.

Nottingham's Michael Holt will provide the second round opposition for Stephen Hendry after beating Belfast's Joe Swail 5-3.

Also on Sunday, Thailand's James Wattana reached the last 32 with a hard fought 5-3 defeat of Glasgow's Drew Henry.

Sunday's results:

First round: J Perry (Eng) 5-3 M Judge (NI)
D Harold (Eng) 5-3 D Roe (Eng)
J Wattana (Tha) 5-3 D Henry (Sco)
M Holt (Eng) 5-3 J Swail (NI)

Second round:
S Murphy (Eng) 5-4 S Davis (Eng)
J White (Eng) 5-3 P Wallace (NI)
C Small (Sco) 5-4 S Pettman (Eng)