Ashton powers on while Saints make a mess of Bath engine room

Referees in the Aviva Premiership are committed to a zero-tolerance policy when it comes to scrummaging offences and, as Bath discovered to their acute discomfort last night, no official on earth is less tolerant than Chris "Zero" White. A good West Countryman he may be, but that did not stop him making the visitors pay through the teeth, both for their indiscipline and for their weakness.

As a result, Northampton muscled their way to a deeply impressive bonus-point victory and underlined their credentials as title candidates.

White dispatched David Wilson, the England prop, to the sin-bin for "lazy running" a few minutes after the interval, which was just about the worst thing that could have happened to a Bath set-piece already under extreme pressure. During Wilson's incarceration, the Saints made an unholy mess of their opponents. By the end, it was too one-sided for words.

A number of clubs struggled for business over the first fortnight of the season, primarily because of a significant expansion of live television coverage and a series of daft kick-off times, but with Northampton rugby on such a high these days there was never much risk of Franklin's Gardens failing to sell out for a floodlit fracas involving the top two sides in the table.

The early tackling lived up to expectations, too, with James Downey and Phil Dowson setting about Bath's outside backs with something approaching bloodlust and helping the Midlanders to exert immediate authority.

Unsurprisingly, it was the ever-threatening Chris Ashton who had the crowd on their feet initially, chipping past Shontayne Hape and haring towards the right corner, only to be dragged to earth by the new man in the England midfield. Hape escaped punishment – heaven knows how – and the injustice of it all put Ashton in a rare old strop.

He might have said one word too many to referee White had Dylan Hartley, his captain, not waved him away. The words "pot" and "kettle" sprang immediately to mind, but the Test hooker certainly did his colleague a favour. This new-found talent for diplomacy was not the only impressive aspect of Hartley's display, either.

He scrummaged as strongly as anyone, found his line-out jumpers with a reasonable degree of accuracy and generated some serious heat in the loose. He was also central to the opening try, completed by Dowson from close range. Twice, Hartley hammered into the Bath defence, taking ball and tackle simultaneously; twice, he performed minor miracles by hanging on to the pass and recycling at the optimum moment.

Shane Geraghty, a rare talent with ball in hand but one of life's hit-and-missers with goal-kicking, had already landed two excellent right-sided penalties, but he missed the conversion from an unchallenging position. Bath might have capitalised instantly, but Olly Barkley hit the crossbar with a shot from distance.

That was followed by a rare misjudgment from the visiting captain, Luke Watson, who butchered a stone-cold overlap by throwing a cut-out pass to Tom Biggs instead of moving the ball through all available pairs of hands. Thus did Wilson's startling 30-metre break – perhaps the longest of the unusually substantial prop's career – come to nothing.

Barkley did manage a penalty with the last kick of the half, but Northampton pretty much topped and tailed things within 30 seconds of the restart when Dowson attacked off the back of a maul and freed Ashton on a 50-metre glory run to the line.

If Geraghty's fluffed conversion was predictable, his preference for more testing penalty kicks bore fruit once again when a finely-judged strike from right field opened up a 16-point gap. Deathly slow on his approach to the ball, he was clearly more comfortable with kicks that could not be charged.

Not that his kicking frailties mattered. Ashton scored again down the right during Wilson's spell in the cooler, and when the wing hobbled off a few minutes later his replacement, Joe Ansbro, claimed a fourth try in the same spot. Ben Williams' consolation score at the fag-end of the contest was irrelevant; this was Saints' night.

Northampton: Tries Ashton 2, Dowson, Ansbro; Conversion Myler; Penalties Geraghty 3. Bath: Try Williams; Conversion Vesty; Penalty Barkley.

Northampton: B Foden; C Ashton (J Ansbro, 59), J Clarke, J Downey, B Reihana; S Geraghty (S Myler, 65), L Dickson (R Powell, 73); S Tonga'uiha (R Dreyer, 73), D Hartley (capt, B Sharman, 65), B Mujati (E Murray, 56), C Lawes (C Clark, 68), C Day, P Dowson, T Wood (M Easter, 73), R Wilson.

Bath: N Abendanon (J Cuthbert, 76); M Carraro, S Hape, O Barkley (B Williams, 56), T Biggs; S Vesty, M McMillan (M Claassens, 67); D Barnes (N Catt, 56), P Dixon (R Batty, 62), D Wilson, (D Bell 79), S Hooper, D Grewcock, A Beattie (Bell, 51-64), L Moody (J Ovens, 70), L Watson.

Referee C White (Gloucestershire).