The 28-year-old from Leamington Spa took control from the opening leg of the contest to record a convincing victory over the world No 1 and England captain. Beaton turned professional only nine months ago, but proved much the calmer of the two players, winning the first set in three straight legs.
He took the second set 3-1, and although Priestley took the third, 3-2, Beaton regained his touch to take the fourth 3-0 for the most significant victory of his career.
Bob Anderson, the 1988 champion, displayed his usual steadiness to beat the five-times winner, Eric Bristow 3-0.
Bristow averaged only 28.47 a dart, despite having five 180s, and in the penultimate leg missed eight successive doubles. Alan Warriner, the fifth seed, recorded a 3-1 win over Scotland's Ronnie Sharp to reach the quarter-finals for the third successive year.
EMBASSY WORLD PROFESSIONAL CHAMPIONSHIP (Frimley Green, Surrey) First round: R Barneveld (Neth) bt G Miller (Eng)
3-2; M Phillips (Wal) bt D Kelly (US) 3-1; J Lowe (Eng) bt C Johns (Wal) 3-1; K Spiolek (Eng) bt K Kenny (Eng) 3-1; P Taylor (Eng) bt J O'Shea (Irl) 3-0. Second round: S Beaton (Eng) bt D Priestley (Eng) 3-1; B Anderson (Eng) bt E Bristow (Eng) 3-0; A Warriner (Eng) bt R Sharp (Scot) 3-1; W Weening (Aus) bt A Anstey (Can) 3-0.Reuse content