|Portugal Masters first-round leaderboard|
|-10 L Johnston (Sco); -9 J Guerrier (Fra); -7 L Canter (Eng); -6 J Caldwell (NI); -5 G Coetzee (SA), M Jordan (Eng), S Soderberg (Swe), T Olesen (Nor); Selected others:-3 T Fleetwood (Eng); -2 J Donaldson (Wal); +5 S Gallacher (Sco)|
Scotland's Liam Johnston "had no idea" he was in contention for a 59 at the Portugal Masters before carding a 10-under-par 61 to lead on day one.
The 27-year-old's 10-birdie score - his lowest on the European Tour - has him a shot clear of France's Julien Guerrier.
Johnston needed a 3-3 finish to become only the second player on the main circuit to break 60 but left his eagle putt on the par-five 17th just short.
"I don't see a round like this coming, but I have been playing well," he said.
"I told my coach back home I was swinging it as good as I have. More importantly, I'm in a really good place mentally."
Johnston has never won on the European Tour and currently does not hold full playing rights, having lost his card in his debut season last year.
On the chance to emulate Oliver Fisher on the same Villamoura course where the Englishman posted 59 two years ago, Johnston said: "I had no idea. I thought it was a par 72, but I was obviously trying to hole the putt on 17 for eagle."
England's Laurie Canter is two strokes off the pace in third after a 64, with Jonathan Caldwell of Northern Ireland a further shot back.