On his 52nd birthday, the New Zealander mixed four birdies with a bogey as he posted a three-under 68 that moved him to four under early on day two before overnight leader Miguel Ángel Jiménez struggled to a 76 that left him four back.
Alex Cejka recovered from a triple-bogey seven midway through his second round to card a 71 on another challenging day of links golf in Wales and he sits at three under in second place.
That was one shot better off than Greig Hutcheon, who is making his Senior Open debut, with 2016 champion Paul Broadhurst, Vijay Singh, Paul Lawrie and Anders Hansen at one under.
Alker is making his first appearance at Royal Porthcawl – a venue which has previously hosted Europe’s only Senior Major in 2014 and 2017 – but is “relishing” the challenge.
“Had two days plodding away, taking my chances when I could on the odd par 5 and odd par 4,” he said.
“Different wind today. Switched around a little bit from a couple different directions.
“It was actually fun. It was enjoyable. I actually love playing links golf and kind of relishing it to be honest.
“I think I’ve hit everything in my bag this week, and that’s a good sign. That’s the sign of a good golf course when you hit every club in your bag.”
Cejka made three birdies in his opening seven holes as briefly moved into the lead at six under, but his momentum was blunted by a seven at the par-four ninth.
The German, a two-time Senior Major winner, dropped another shot at the 16th but regained it with a two-putt birdie at the 18th which for the second day running played as the easiest hole on the course.
“I had a good start,” he reflected. “Made a couple birdies. Then I was uncomfortable on the 9th hole.
“The wind was left-to-right and I maybe should not have hit driver, but I blocked a little bit right and it found the bushes.
“So I had to take an unplayable, pitch out on the green, three-putt. That stung a little bit after making three birdies earlier.
“But I fought back on the back nine that’s playing a little bit trickier with the wind. I had a couple good chances but I’m happy that I finished with a birdie or an eagle putt.”
Both Alker and Cejka had formed part of the morning wave, while Hutcheon was a late starter on day two.
Beginning the round at one under, the Scot made a blistering start with four birdies in his opening six holes as conditions calmed before two further gains in his final four holes when the winds had picked up again helped him to a 68.
The three-time European Challenge Tour winner, who played at The Open in 1998, said: “I kind of noticed my name on the leaderboard out of the corner of my eye, and I think I might have got a little bit of leaderboard altitude sickness and had a really nervy three-putt on 7.
“But I steadied myself and I played quite well. You can only do your best, and some holes are just so difficult, you can hit good shots and you just get into trouble in the fairway bunkers and so on.
“So, I think you’ve just got to be prepared to make bogeys, especially when the wind gets like this.”
Both Broadhurst and Lawrie mixed two birdies with two birdies in their 71s on Friday, Singh carded a 72 while Hansen, a three-time DP World Tour winner, climbed 15 places on the leaderboard with a two-under 69.
Jiménez held a two-shot lead when he hit the turn but dropped seven shots in eight holes from the tenth before birdieing the 18th to end the day in an eight-strong group on level par which also includes Bernhard Langer and Colin Montgomerie.
Defending champion Darren Clarke made the cut on the number at five over after a 74, while Rich Beem is at four over after he ensured his progress with a crowd-pleasing birdie at the 18th.
Past winner Stephen Dodd, Legends Tour Order of Merit leader Adilson Da Silva, Ian Woosnam and José María Olazábal were among those to miss out on the weekend’s action.
