Ben Duckett blasted a brilliant career-best 178 not out as Northants got the new season off to a flying start against Sussex at the County Ground.
Alex Wakely added 51 and on-loan Nottinghamshire opener Jake Libby hit 42 as Northants made the County Championship Division Two title favourites toil in the field.
Duckett was the star of the show, hitting 28 fours and one six in his innings, which will rumble on into day two.
And the 21-year-old said: “I’m pretty chuffed. The job isn’t done, I’ve still got to try and go past 200 tomorrow. There were games last year when I was frustrated, getting out when set to go and make a huge score so it’s a great chance to do it on day two.
“There was a bit of nip early on and Steve Magoffin bowled really well. But the plan was to play as straight as possible and stay patient and we managed to do that.”
The first day was eventually ended by bad light, with Duckett and Josh Cobb (9no) at the crease.
Northants already have two batting points from 82 overs, while Sussex were struggling with the ball, with Steve Magoffin and Danny Briggs the only bowlers able to break through.