PRETORIA, February 27, 2014 (AFP) - The 36-year-old snatched seven birdies in a flawless trek over the 7,281-metre (7,964-yard) The Els Club Copperleaf course west of Pretoria.
Designed by South African quadruple Major winner Ernie Els, it is the longest European Tour layout, but Dyson sparkled on his back nine with four consecutive birdies from the 15th hole.
His round left him one stroke ahead of South Africans Jared Harvey and Erik van Rooyen and Englishman Ross Fisher in a first round that ended an hour early due to lightning.
Dane Lucas Bjerregaard, Indian Shiv Kapur and Englishman Chris Wood were a further shot back on 67 in the last of eight South Africa-based 2014 European events.
Dyson was fined 30,000 pounds (50,000 dollars-36,000 euros) and got a suspended two-month ban last year after tapping down a spike mark during a tournament in China.
The blond Cheshire-based golfer called it the "lowest point of his career", but he had cause of happiness on a warm, partly cloudy late South African summer afternoon.
"It was a lovely start to claim my lowest round in quite a few years. It puts you in a good frame of mind ahead of the weekend," he said.
"Putting has been the problem for the last few weeks so my caddie and I had a chat about what I am doing wrong.
"We spent about 90 minutes on the putting green yesterday (Wednesday) and I managed to get a good feel for it," he said.
South African Dawie van der Walt made a disastrous start in defence of the title, lying five over after 16 holes when play was suspended.
Leading clubhouse scores after storm-interrupted first round of European Tour-Sunshine Tour co-sanctioned Tshwane Open golf tournament at par-72, 7,281-metre (7,964-yard) The Els Club Copperleaf near Pretoria Thursday (RSA unless noted):
65 - Simon Dyson (ENG)
66 - Ross Fisher (ENG), Jared Harvey, Erik van Rooyen
67 - Lucas Bjerregaard (DEN), Shiv Kapur (IND), Chris Wood (ENG)
68 - Jacques Blaauw, Magnus Carlsson (SWE), Jean Hugo, Daan Huizing (NED), Shane Lowry (IRL), Carlos del Moral (ESP), Ricardo Santos (POR), Anthony Wall (ENG)
69 - Merrick Bremner, Heinrich Bruiners, Jorge Campillo (ESP), Jack Doherty (SCO), Michael Hoey (NIR), David Howell (ENG), Brandon Pieters, Ruan de Smidt, Andy Sullivan (ENG), Peter Whiteford (SCO)