Guepy did not play golf until he was 20 because, in his teens, he concentrated on tennis, at which he was good enough to be the fifth best junior in Australia and later among the top 20 juniors in France.
Guepy, now based in Bordeaux, had eight birdies and an eagle in his round but also four bogeys and one double bogey. 'It was a real crazy round,' he said.
Guepy went out in a six-under- par 30 at which point he was 11 under and four ahead of the field but dropped two shots on the final four holes. 'It was very difficult against the wind coming home and I got very tired,' he said.
He still finished two shots clear of Wayne Riley and Rolf Muntz, the former British Amateur champion from the Netherlands. Howard Clark and Gordon J Brand were among the best-placed Britons in joint 12th place on 141.
HEINEKEN CATALONIA OPEN (Pals) Leading second-round scores (GB or Irl unless stated): 135 J L Guepy (Fr) 67 68. 137 R Muntz (Neth) 72 65; W Riley (Aus) 68 69. 139 F Nobilo (NZ) 71 68; R Goosen (SA) 74 65; J Coceres (Arg) 70 69. 140 J Townsend (US) 73 67; J Quiros (Sp) 72 68; C O'Connor Jr 70 70; J Rozadilla (Sp) 73 67; M A Jimenez (Sp) 70 70. 141 C Brooks 74 67; H Clark 69 72; G J Brand 69 72; A Collison 72 69.Reuse content