Toby Roland-Jones finished with a match haul of 12 wickets as Middlesex blew away Northamptonshire by an innings and 84 runs to go top of the LV= County Championship Division One.
Roland-Jones' career-best match figures of 12 for 105 helped his side complete a convincing victory as the hosts were bowled out for 176 in 87.5 overs at Wantage Road.
The 26-year-old's return of six for 50 also equals his best figures for a single innings.
The win is Middlesex's fourth from their six matches so far and means they move 19 points clear of second-placed Yorkshire, who have a game in hand.
Marcus Trescothick looked at his vintage best as Somerset moved within sight of a convincing victory over Durham at Taunton.
The former England opener was unbeaten on 58 and had been well supported by Johann Myburgh (48 not out) as Somerset reached 112 without loss at the close of day three, chasing a target of 248.
A century from Michael Richardson had earlier given Durham hope of pushing for victory themselves but some inspired bowling by Craig Overton (five for 63) limited the champions to 326 in their second innings.
Matt Coles starred with bat and ball as Hampshire returned to the top of Division Two with a comprehensive 278-run over Leicestershire at Grace Road.
The former Kent all-rounder plundered a quick-fire 83 in the visitors' second innings, then claimed three for 24 with the ball as the Foxes slipped to a first defeat of the season.
Hampshire had briefly been replaced at the top of the table when Worcestershire completed a three-day victory over Essex on Tuesday, but leapfrogged their promotion rivals after claiming 22 points from this match.
Gloucestershire registered what was a comprehensive first win of the season as they wrapped up a 290-run triumph over Kent at Bristol.
The visitors began the day on 165 for five and needing an unlikely-looking 417 more runs for victory, and although they put up resistance - led by Ben Harmison, who fashioned a career-best 125 - for a while, their defeat was soon sealed.
Matt Taylor took three wickets as Gloucestershire dismissed their opponents for 291, completing the task during an extra half-hour added to the morning session.