On the final day, 3 wickets from each of Dominic Cork and Muttiah Muralitharan helped dismiss Worcestershire for 191 runs, with David Wigley unable to bat because of a broken hand sustained when James Anderson bowled a beamer at him in the first innings.
Northamptonshire won the toss and batted, but 215 for 7 was never going to be enough on a fine Old Trafford pitch, where Lancashire's Mal Loye smashed 94 not out with ten fours and three sixes.
Dominic Cork was the most punishing bowler, taking four for 14 off nine overs (including five wides) as Gloucestershire whimpered to 86, as veteran wicketkeeper Mark Alleyne top-scored with 24 not out.
Jon Lewis, who had earlier on in the day been called up to the England ODI squad to meet Bangladesh and Australia, took three for 40, but it was not enough to stop Lancashire from cruising to the target with nearly 25 overs to spare.
Yorkshire's 335 in reply included solid innings from Phil Jaques, Craig White and Michael Lumb, while Lancashire's James Anderson took four wickets.
Yorkshire fell to 182 for 8 before a resistant 64 not out from Matthew Hoggard (only his second half-century of his career) saved the draw, as he shared partnerships of 45 for the ninth wicket with Richard Dawson and 46 for the tenth with Deon Kruis.
Winning the toss and batting, Derbyshire had a good opening partnership between Australian Michael Di Venuto and Ben France, but Greg Chapple put the pressure on with some patient, economical bowling and reaped the rewards with three wickets for 29.
Lancashire thought that would be a walk in the park, especially as Iain Sutcliffe and Mal Loye paired up for 53 for the second wicket, but they then lost seven men for sub-12 scores and were in trouble at 131 for 9.
(Cricinfo scorecard) Lancashire recorded six wins in their first seven games, only losing to Nottinghamshire Outlaws, but beating Roses rivals Yorkshire Phoenix twice.
Matthew Hoggard, the England Test bowler, showed an uncanny knack of being uneconomical, conceding 65 runs in his four overs, and despite two wickets he lost the game for the Phoenix.
Despite Ian Harvey digging into them with two wickets, the early run-rate ensured that Lancashire set a target of 208, Law recording the second Twenty20 century this season – in 56 balls.
They followed that up with quarter-final wins in the Twenty20 Cup and C&G Trophy, before suffering their first loss of July with an eight-wicket League defeat to later champions Essex Eagles.
Three months earlier, Michael Hussey, Paul Collingwood and Steve Harmison had been firing for the Durham lads as they beat Leicestershire by an innings and 216 runs, the highest margin of victory in the County Championship so far this season – before this match.
(Cricinfo scorecard) Lancashire beat Sussex by 35 runs to progress to the Semi-Finals of the C&G Trophy Andrew Symonds scored 101 and took two wickets for 46 to be the difference between the sides at Old Trafford.
Having been sent in to bat, Lancashire owed much of their success to a partnership of 118 between Symonds and Marcus North, and good lower-order hitting took the total to 249 for 8, despite three wickets each from Sussex' Pakistanis, Rana Naved-ul-Hasan and Mushtaq Ahmed.
The Sussex chase looked on when they were 112 for 1 with Matt Prior and Chris Adams at the crease, as they were just waiting for opportunities to up the run-rate, but instead Symonds and England all-rounder Andrew Flintoff ran through them with the ball, and Robin Martin-Jenkins and Ahmed eventually had to consolidate to 214 for 8, losing by 35 runs.
Derbyshire needed some big hits from the specialist bowlers in the end, and crumbled to 172 with three balls remaining, James Anderson getting the honour of taking the last wicket.
Lancashire number three Mal Loye replied with 194 after Andre Adams had dug out the hosts' captain Mark Chilton for 4, as the match ground towards an inevitable draw, Loye spending 200 balls for his century and eventually spending nearly eight hours at the crease before being caught by Alastair Cook off Grant Flower, six runs short of what could have been his second double century in July 2005.
Lancashire eventually batted out a mammoth 220.3 overs – Danish Kaneria bowling 70.2 of those without a single wicket – to make 655 for 6 before the captains agreed to a draw.
(Cricinfo scorecard) August began with a seven-wicket loss in a one-day tour match to Bangladesh A, before a 234-run Championship win over Leicestershire sent them second in the table with a game in hand.
Medium pacer Ryan Cummins got three for 32 in his first game for Leicestershire, but only bowled ten overs, as the captain preferred an ineffective but economical Claude Henderson.
Wood made 86 and White 110 not out, while the Lancashire captain Mark Chilton was stumped for options and had to turn to part-time spinner Marcus North for seven overs of bowling – which yielded the wicket of Ismail Dawood.
The Gladiators won the toss and got immediate success, as Jon Lewis dismissed Mal Loye with the second ball of the day, but pretty much everything went against Gloucestershire from then on, as Stuart Law, Mark Chilton and Andrew Symonds flayed the bowling to all corners.
Ben Smith and Vikram Solanki fought back, however, pairing up for 140 for the fourth wicket, and Worcestershire looked confident of avoiding the follow-on with the score on 330 for 4.
Northamptonshire were bowled out early on the second morning for 289, but immediately hit back, Damien Wright dismissing Lancashire's captain Mark Chilton for 0.
On the second day, Andrew Symonds and Glen Chapple both made fifties, sharing a 136-run stand with sent Lancashire to 340 – before spinners Middlebrook and Danish Kaneria removed the last four wickets for no further score.
Sajid Mahmood then took two on the third day to finish Essex off for 227, setting Lancashire 155 to win, and a 106-run opening stand between Mark Chilton and Iain Sutcliffe brought them to the brink.
The Lightning fell to 94 for 5, with four Middlesex bowlers getting one wicket each, and despite all-rounder Glen Chapple recording his first one-day half-century of the season with 71, and they were bowled out for 219 an over before the end.
An opening partnership of 63 saw Leicestershire take the lead, but spinners Murali Kartik and Andrew Symonds took two wickets each, while the three seamers Chapple, Sajid Mahmood and Anderson took one each to round off the day.
However, England Under-19 prodigy Stuart Broad removed three men for five runs with his seam bowling, and wickets fell regularly after that – Dinesh Mongia and Charl Willoughby taking two each.