Bjorn blazes to Wentworth lead
Bjorn hailed the best round of his entire career after carding a brilliant 62, a round completed just moments before the first of two suspensions of play due to the threat of lightning which left 33 players unable to complete their rounds.
"I was signing my scorecard when the siren went and Stephen Gallacher looked at me and says, 'You're not having a very bad day, are you?'" Bjorn said. "We could kind of feel there was something going on in the weather, so it was nice to get in."
At 10 under par, Bjorn held a two-shot lead over Ireland's Shane Lowry, with Spain's Rafael Cabrera-Bello on seven under and the likes of Henrik Stenson, Martin Kaymer and Rory McIlroy all four under.
Bjorn missed the cut in last week's Spanish Open and feared the worst in a tournament where he has produced just one top-10 finish - in 1998 - in 16 previous appearances.
"You shoot great rounds in your career but to shoot 62 on this course, you can't ask for more," said Bjorn, who went on to win the European Masters in 2011 the last time he shot 62 on the European Tour.
"I don't really know where to start. Last week was awful and I was starting to feel a little frustrated with things. Practice this week I was not good either.
"To step out on this course of all courses and play like I did today was surprising. Although I lived here for nine years it's not a place where I think it's going to be a great week, but I have to stick my head down now and focus on the rest of the week."
Bjorn, who looks set to qualify for his first Ryder Cup appearance since 2002, birdied the second, fourth and seventh to reach the turn in 32 before a superb scoring burst on the back nine.
The 43-year-old birdied the 10th and 11th and holed from just six feet for an eagle on the par-five 12th, before picking up further birdies on the 14th, 16th and 18th.
Asked to explain his renaissance after falling out of love with the game five or six years ago, Bjorn added: "Hard work. Determination to not let a golf career fade away. I've just been determined to get myself to where I can play with the best in the world and I'll keep continuing to do that as long as my body allows me to.
"I enjoy being out here, which I probably didn't do for a couple of years. It's very easy when you get past 40 to stop enjoying this after a long career. I have travelled with my golf clubs since I was 14 years old and sometimes you forget why you love the game and it becomes hard work."
Bjorn is currently third in the Ryder Cup qualifying race but added: "I still think I need to do a lot more. There's a lot of guys playing great golf at the moment and over the last few weeks a few names are all starting to come back into the frame.
"I've watched a lot from the sidelines (he has been vice-captain three times) and that can hurt a little bit, but I wanted to play in another Ryder Cup and I've got to stay focused and determined to keep playing good golf to get there."
Lowry's round was twice disrupted by the bad weather, but the 27-year-old - who won the Irish Open as an amateur in 2009 - was not about to say a bad word about the tournament.
"I love it around here," said Lowry, who was fourth in 2011 and 12th last year. "It's a great event. It's a great golf course.
"I've been struggling and my best finish this season was last week, tied 15th in the Spanish Open. I've missed a few cuts and haven't really been putting that well but I managed to find something at home a couple of weeks ago and hopefully can keep it going.
"I went back to an old putter that I used years ago and it brought back good memories maybe."
A knee injury forced Sergio Garcia to retire from the tournament after an opening round of 73, while defending champion Matteo Manassero slumped to an eight-over-par 80 which included two double bogeys and a nine on the 17th.