Opener Emilio Gay scored a commanding 165 not out, his fifth first-class century, as Northamptonshire capitalised on being put into bat against Middlesex. The hosts finished day one of this Vitality County Championship match at Wantage Road in a dominant position on 311 for three.
Gay, who turned 24 on Sunday, celebrated his birthday early by scoring his highest first-class score off 272 balls with 17 boundaries.
He found a supportive partner in his skipper Luke Procter, who hit 73 in a 189-run stand in 65.2 overs, surpassing Northamptonshire's previous highest second-wicket partnership against Middlesex (179) established by Stephen Peters and Alex Wakely in 2010.
Middlesex's bowlers inserted Glamorgan at Lord's last week and were punished. They stuck diligently to their task on a largely docile wicket, deploying the short ball as the day wore on in a bid to make inroads with the Kookaburra ball.
Ryan Higgins removed opener Jason Broad lbw in the second over of the day, giving the bowlers cause to celebrate. The next breakthrough did not come until after tea, when Procter and Gay took control.
After Procter was dismissed by spinner Josh de Caires, Gay and Karun Nair (41) shared an 86-run partnership. However, Nair played on to a delivery that jagged back from Toby Roland-Jones.
It was also a memorable day for Northamptonshire as they secured their first home batting points of the season.
Procter continued his good form after scoring 92 against Sussex. He was strong in defence but also played some attacking shots during the morning session. He drove his opponent Roland-Jones down the ground and hit Tom Helm through square for four.
Gay initially struggled outside off-stump, playing and missing against the seamers when they found some movement. He improved as the game went on, playing some attractive shots off his legs, taking on the short ball, and driving firmly down the ground. One highlight of the morning session was a stylish four through the covers off Helm.
The pair had taken Northamptonshire to 106 for one at lunch. It seemed they would continue scoring at the same pace after the break as Gay disdainfully pulled Helm through midwicket.
Scoring slowed significantly, with only 24 runs in the first hour of the afternoon. Procter became increasingly comfortable in the forties, eventually reaching his half-century from 126 balls.
As Middlesex bowled short, Roland-Jones struck Procter under the armpit, but otherwise, the Northamptonshire captain was content to duck out of the way. Gay took a more attacking approach. His pull shots were mostly well-controlled, although he did occasionally keep the leg-side fielders on their toes.
As tea approached, the scoring rate increased. Procter took full advantage of a full toss from de Caires and smote it over midwicket for the first six of the innings.
Gay then hit his ninth boundary, rocking back and slashing Higgins through point, to reach three figures in style.
After the interval, Procter drove another de Caires full toss to the ropes, but when he attacked the spinner's next over, he could only pick out Helm at mid-on to leave Northamptonshire on 190 for two. He hit six fours and a six from 194 balls.
Karun Nair hit a four behind square off de Caires, but Helm troubled him with a couple of well-directed short balls. Nair fended one away, which fell safely between a group of advancing close catchers. He found success with the sweep and reverse sweep, taking consecutive boundaries off de Caires and soon settling into the groove.
Gay, on the other hand, continued to play his shots, backing away to slice Helm through the covers and using his feet to drive de Caires through the same area.
As Northamptonshire approached 250, Middlesex took the new ball. Ethan Bamber and Roland-Jones found helpful movement off the seam, but Gay appeared untroubled. He played an exquisite shot off his legs and a glorious cover drive shortly before stumps.