Broadhurst, whose last European Tour title came at the 1995 Open de France, finished with a 54-hole total of 11-under-par 205.
Barry Lane, who played alongside Broadhurst on Saturday, posted a 67 to join Eduardo Romero in a tie for second at 10-under-par 206. Overnight leader Patrik Sjoland was one shot further back at 9-under-par 207.
'We just plodded around,' said Broadhurst. 'You really didn't notice the weather.'
Broadhurst, a four-time winner on the European Tour and a former Ryder Cup member, picked up a birdie on the opening hole at the Forest of Arden but gave that shot back with a bogey at the second.
He recovered well with a birdie at the fourth and added back-to-back birdies from the par-4 sixth to jump to 8 under.
Broadhurst bogeyed the ninth but dropped his second shot inside 13 feet at the following hole. The 38-year-old drained the putt for a birdie at the 10th and made his move to the top of the leaderboard a few holes later.
Broadhurst ran off three consecutive birdies starting at the par-5 12th and parred his way in to hold the lead heading into the final round of a European Tour event for the first time since the 1998 Deutsche Bank - SAP Open.
'It's been a long time since I was last leading,' said Broadhurst. 'The last six rounds I have played have all been under-par by at least two so I am on a decent run. If I can keep that going tomorrow it might be enough.'
Lane would also like to make a return trip to the winner's circle. The 43- year-old, who has not won on the European Tour in over 10 years, had an eventful front nine on Saturday with four birdies and two bogeys.
He added birdies at 12 and 14 before finding trouble with a bogey at the 16th. Lane countered with a birdie at the very next hole and knocked his tee shot to 8 feet at the par-3 18th.
Lane converted the putt for a closing birdie and a share of second with one round to play.
Romero, senior to both Lane and Broadhurst, could become the oldest player to win on the European Tour should he prevail on Sunday.
The Argentine, who was penalized two strokes on Friday, parred his first five holes before his approach to the sixth stopped within 14 feet of the hole. The 49-year-old sank the birdie putt but stumbled to a bogey at the 10th after he failed to convert a short putt for par.
Romero responded at the par-5 12th and left his third shot inside 8 feet for a birdie. He putted from off the green for a birdie at the par-3 15th to join Broadhurst at 11 under but faltered with a bogey at the following hole en route to a round of 71.
Fellow Argentine Angel Cabrera, who was in contention last week at the Italian Open, posted a 70 to take fifth place alone at 8-under-par 208.
Alastair Forsyth, Nick O'Hern and Martin Maritz shared sixth place at 7-under-par 209.