Wasps emphatically ended Northampton's Zurich Premiership title hopes for a second successive season as they booked their place in the Twickenham Grand Final against Bath.

The reigning league champions sent Saints packing from a sun-drenched Causeway Stadium, keeping their domestic and European double bid firmly on course.

Wasps, Heineken Cup finalists against French giants Toulouse next Sunday, booked themselves a Twickenham return six days later after halting a recent run of poor Premiership form.

They recovered brilliantly from a subdued opening 30 minutes to blitz Northampton with three tries before half-time.

Wing Tom Voyce did his England summer tour prospects no harm at all in front of watching England coach Andy Robinson by scoring a stunning solo try, while there were also touchdowns for skipper Lawrence Dallaglio and replacement centre Ayoola Erinle.

Northampton, desperate to give departing coach Wayne Smith a Twickenham send-off, led until the 32nd minute through two Bruce Reihana penalties, but they had no answer once Wasps moved out of second gear.

Saints, beaten by Wasps at the same play-off semi-final stage last term, were killed off through centre Stuart Abbott's 75-metre interception try midway through the third quarter, and then it was nothing more than damage limitation.

Flanker Andrew Blowers collected a consolation try, converted by Reihana, only for back-row forward Paul Volley to claim Wasps' fifth touchdown following a strong Josh Lewsey run, when he brushed aside Ben Cohen's attempted tackle.

An 80-metre breakaway launched by Mark Denney enabled Voyce to claim his second touchdown, then prop Tim Payne's close-range effort made the try-count 7-1, prior to Saints wing Nick Beal's late effort that Shane Drahm converted, but Dallaglio's second try completed the rout.

Wasps full-back Mark Van Gisbergen finished with seven conversions, and fly-half Alex King kicked a penalty as Wasps stormed home.

The only disappointment, given scorching weather, was a poor crowd of just over 6,000, which again put a question mark over English rugby's contentious play-off system.

Wasps scrum-half Rob Howley went into the game amid speculation about his playing future, fuelled by rugby director Warren Gatland's admission that talks had been held with Saints' England World Cup scrum-half Matt Dawson.

Former Wales captain Howley will undergo wrist surgery next month, and is not expected to play again until at least October, which has sparked Wasps' interest in Dawson.

Dawson, capped 62 times by England, sat out Sunday's clash because of a calf-muscle injury, and has probably played his last game for Northampton following a 12-year stint at Franklin's Gardens.

Four Saints players - Beal, John Leslie, Mark Connors and Jon Phillips - featured for the final time before their confirmed departures, while Volley made a last home appearance prior to joining French club Castres this summer.

Northampton, crushed 31-5 by Wasps on the same ground just six weeks ago, displayed an immediate thirst to avenge that result, and two Reihana penalties inside the opening 10 minutes rewarded their territorial dominance.

Wasps took time to settle, and although King slotted a 14th-minute penalty, he was wide of the target five minutes later, before Saints surged back upfield and Grayson drifted a drop-goal attempt narrowly wide.

But Northampton were stung eight minutes before half-time, when Voyce conjured up a candidate for try of the season.

The former Bath wing received possession 10 metres inside his own half and set off on a weaving run before rounding Reihana on the outside. Cohen cut him down with a superb tackle at the corner flag, but video official Ed Morrison ruled that Voyce had not slid into touch, and Wasps were ahead.

King could not add the touchline conversion, and Wasps suffered an immediate injury blow when centre Fraser Waters departed nursing a hamstring twinge. He was replaced by Erinle.

Wasps were now firmly into their stride though, and they added a second try as half-time approached.

Lock Simon Shaw drove powerfully from a line-out, allowing just enough room for Dallaglio to crash over, with referee Chris White once again requiring confirmation from Morrison before awarding the score.

Van Gisbergen took over the kicking duties, and he landed the wide-angled conversion to give Wasps some breathing space.

But there was more time during first-half injury time. Northampton's defence again found itself at sixes and sevens, as Shaw delivered a scoring pass to Erinle, who effortlessly evaded Reihana's poor attempted tackle.

Van Gisbergen's second conversion gave Wasps a 22-6 interval advantage, putting Twickenham within sight and Northampton firmly on the back foot.

Saints bravely tried to claw their way back, but scrum-half Mark Robinson's intended pass to centre Mark Tucker was cut out by Abbott, who sprinted clear and ended the game as a contest.

With the game won, Gatland substituted the likes of Howley, Abbott, Shaw and hooker Trevor Leota as minds began diverting to next week's mouthwatering Toulouse showdown.