Saracens moved back to the top of Pool 5 thanks to a hard fought 31-26 victory over the Ospreys in a stunning game at Wembley.

Welsh prop Rhys Gill scrambled over for the opening score after two minutes and Owen Farrell had no problem adding the extras with the boot.

Dan Biggar and Farrell then exchanged penalties before Ospreys centre Ashley Beck grabbed his side's first try and Biggar's conversion levelled up the scores.

But the English Champions soon forced their way back in front courtesy of a try from Ernst Joubert

Biggar added his second penalty but six points from Farrell before the interval gave the hosts a commanding position going into the tunnel.

The Ospreys needed to score first at the start of the second period and they did exactly that with Biggar slotting home another penalty for the Welsh side.

Saracens wing Chris Wyles crossed for Saracens' third try and Beck then collected his second score for the Ospreys.

Farrell and Biggar exchanged further penalties but Saracens held on to take the victory.

In Italy Treviso stormed to an unlikely 30-26 victory over Biarritz, maintaining their unbeaten home record in the tournament this season.

Following up from their impressive draw against the Ospreys in Round 2, flyhalf Kristopher Burton inspired Treviso to victory in northern Italy.

Elsewhere Gloucester edged a win over Connacht 14-10, making it third time lucky in Europe, while Connacht must still wait for a first Heineken Cup win.

In a nail-biting encounter at the Galway Sportsground it was the boot of Gloucester flyhalf Freddie Burns that proved the difference, as he slotted three penalties.

Castres Olympique claimed their first victory in this year's Heineken Cup, with a convincing 41-22 win over last season's Heineken Cup finalists Northampton Saints.

In an end-to-end game on entertaining rugby both sides scored four tries but the boot of Romain Teulet proved the difference between the teams.

The visitors couldn't have made a worse start to this contest, when Castres scored their first try in four games after only three minutes when impressive openside flank, Steve Malonga, finished off a sweeping attacking move.

Yellow cards to Steve Myler and Tom Woods proved costly for Saints as they couldn't compete with just 14-men on the pitch for much of the game.

Ronan O'Gara celebrated his 100th Heineken Cup appearance with a 12 point contribution that allowed Munster to march to the top of Pool 1 with a 17-14 victory over the hitherto unbeaten Scarlets.

The home side had a record Heineken Cup crowd to celebrate, 13,183, but after taking an early 8-0 lead they were outmuscled by Paul O'Connell's pack and failed to take their chances.

The Scarlets may have lost Wales wing George North before kick-off, but they still felt they had enough behind the scrum to maintain their winning sequence in the Pool and end a run of 12 successive defeats to Munster.

It was as long ago as the Heineken Cup quarter-final of April, 2007, that the Scartlets last beat Munster and this made it an uncomfortable 13th straight defeat. A 14th at Thomond Park next week could be terminal for their chances of emerging from their Pool in the New Year.

Finally, London Irish remain very much alive in Pool 2 after a superb bonus-point win over Racing Metro in Colombes. The Exiles ran out 34-14 victors at the Stade Yves Dun Manoir to register their first success of the competition.

Previous defeats to Edinburgh and Cardiff Blues looked to have all but ended Irish's hopes of qualification for the quarterfinals but a maximum five-point tally means they are now just two points behind second-placed Edinburgh and five shy of leaders the Blues.

Jonathan Spratt, Joe Ansbro and Adam Thompstone were the try scorers for Toby Booth's men, with left-wing Thompstone grabbing a clinical brace.

Results:

Saracens 31 Ospreys 26

Scorers:

For Saracens:
Tries: Gill, Joubert, Wyles
Cons: Farrell 2
Pens: Farrell 4

For Ospreys:
Tries: Beck 2
Cons: Biggar 2
Pens: Biggar 4

Teams:

Saracens: 15 Alex Goode, 14 David Strettle, 13 Owen Farrell, 12 Brad Barritt, 11 Chris Wyles, 10 Charlie Hodgson, 9 Ben Spencer, 8 Ernst Joubert, 7 Jacques Burger, 6 Kelly Brown, 5 Mouritz Botha, 4 Steve Borthwick, 3 Matt Stevens, 2 Schalk Brits, 1 Rhys Gil.
Replacements: 16 Jamie George, 17 Deon Carstens, 18 Carlos Nieto, 19 George Kruis, 20 Andy Saull, 21 Peter Stringer, 22 Adam Powell, 23 James Short.

Ospreys: 15 Richard Fussell, 14 Tommy Bowe, 13 Andrew Bishop, 12 Ashley Beck, 11 Shane Williams, 10 Dan Biggar, 9 Rhys Webb, 8 Joe Bearman, 7 Justin Tipuric, 6 Tom Smith, 5 Jonathan Thomas, 4 Ryan Jones, 3 Adam Jones, 2 Richard Hibbard, 1 Duncan Jones.
Replacements: 16 Huw Bennett, 17 Ryan Bevington, 18 Aaron Jarvis, 19 Ian Gough, 20 George Stowers, 21 Tom Isaacs, 22 Matthew Morgan, 23 Sonny Parker.

Benetton Treviso 30 Biarritz 26

Scorers:

For Treviso:
Tries: Rizzo, Barbieri, Van Zyl
Cons: Burton 3
Pens: Burton 3

For Biarritz:
Tries: Taele, Bosch, Traille, Lesgourgues
Cons: Baby, Peyrelongue 2

Teams:

Treviso: 15 Luke McLean, 14 Ludovico Nitoglia, 13 Tommaso Benvenuti, 12 Alberto Sgarbi, 11 Brendan Williams, 10 Kristopher Burton, 9 Tobias Botes, 8 Paul Derbyshire, 7 Alessandro Zanni, 6 Robert Barbieri, 5 Cornelius van Zyl, 4 Antonio Pavanello, 3 Lorenzo Cittadini, 2 Enrico Ceccato, 1 Michele Rizzo.
Replacements: 16 Diego Vidal, 17 Ignacio Fernandez Rouyet, 18 Pedro di Santo, 19 Valerio Bernabo, 20 Manoa Vosawai, 21 Marco Filippucci, 22 Edoardo Gori, 23 Alberto Di Bernardo.

Biarritz: 15 Iain Balshaw, 14 Taku Ngwenya, 13 Benoît Baby, 12 Damien Traille, 11 Ilikena Bolakoro, 10 Marcelo Bosch, 9 Yann Lesgourgues, 8 Florian Faure, 7 Talalelei Gray, 6 Wenceslas Lauret, 5 Pelu Taele, 4 Jérôme Thion, 3 Campbell Johnstone, 2 Benoit August, 1 Fabien Barcella.
Replacements: 16 Romain Terrain, 17 Yvan Watremez, 18 Sylvain Marconnet, 19 Jean-Baptiste Roidot, 20 Benoit Guyot, 21 Julien Peyrelongue, 22 Charles Gimenez, 23 Dane Haylett-Petty.

Connacht 10 Gloucester 14

Scorers:

For Connacht:
Try: Duffy
Con: O'Connor
Pen: O'Connor

For Gloucester:
Try: Simpson-Daniel
Pens: Burns 3

Teams:

Connacht: 15 Gavin Duffy (captain), 14 Mark McCrea, 13 Kyle Tonetti, 12 Dave McSharry, 11 Tiernan O'Halloran, 10 Niall O'Connor, 9 Frank Murphy, 8 Ray Ofisa, 7 John Muldoon, 6 Dave Gannon, 5 George Naoupu, 4 Mike McCarthy, 3 Ronan Loughney, 2 Ethienne Reynecke, 1 Brett Wilkinson.
Replacements: 16 Adrian Flavin, 17 Denis Buckley, 18 Rodney Ah You, 19 Mick Kearney, 20 Eoin McKeon, 21 Paul O'Donohoe, 22 Matthew Jarvis, 23 Fetu'u Vainikolo.

Gloucester: 15 Olly Morgan, 14 Charlie Sharples, 13 Henry Trinder, 12 Eliota Fuimaono-Sapolu, 11 James Simpson-Daniel, 10 Freddie Burns, 9 Rory Lawson, 8 Luke Narraway, 7 Andy Hazell, 6 Brett Deacon, 5 Jim Hamilton, 4 Peter Buxton, 3 Dario Chistolini, 2 Scott Lawson, 1 Nick Wood.
Replacements: 16 Matias Cortese, 17 Dan Murphy, 18 Rupert Harden, 19 Will James, 20 Akapusi Qera, 21 Nick Runciman, 22 Tim Taylor, 23 Jonny May.

Castres 41 Northampton 22

Scorers:

For Castres :
Tries: Malonga, Martial 2, Diarra
Cons: Teulet 3
Pens: Teulet 5

For Northampton:
Tries: Sorenson, Elliott 2, Manoa
Con: Myler

Yellow cards: Myler, Wood

Teams:

Castres: 15 Romain Teulet, 14 Romain Martial, 13 Thomas Sanchou, 12 Seremaia Bai, 11 Max Evans, 10 Rémi Tales, 9 Rory Kockott, 8 Chris Masoe, 7 Steve Malonga, 6 Ibrahim Diarra, 5 Rodrigo Capo Ortega, 4 Scott Murray, 3 Luc Ducalcon, 2 Marc-Antoine Rallier, 1 Michaël Coetzee.
Replacements: 16 Mathieu Bonello, 17 Anton Peikrishvili, 18 Rossouw Kruger, 19 Matthias Rolland, 20 Yannick Caballero, 21 Paul Bonnefond, 22 Pierre Bernard, 23 Thierry Lacrampe.

Northampton: 15 Ben Foden, 14 Vasily Artemyev, 13 George Pisi, 12 Tom May, 11 Jamie Elliott, 10 Stephen Myler, 9 Lee Dickson, 8 Samu Manoa, 7 Ben Nutley, 6 Tom Wood, 5 Mark Sorenson, 4 Courtney Lawes, 3 Paul Doran Jones, 2 Dylan Hartley (captain), 1 Soane Tonga'uiha.
Replacements: 16 Mike Haywood, 17 Alex Waller, 18 Brian Mujati, 19 James Craig, 20 James Ingle, 21 Martin Roberts, 22 Ryan Lamb, 23 Jon Clarke.

Scarlets 14 Munster 17

Scorers:

For Scarlets:
Try: Shingler
Pens: Priestland 2, Jones

For Munster:
Try: Ronan
Pens: O'Gara 4

Teams:

Scarlets: 15 Daniel Newton, 14 Liam Williams, 13 Scott Williams, 12 Jonathan Davies, 11 Sean Lamont, 10 Rhys Priestland, 9 Gareth Davies, 8 Ben Morgan, 7 Rob McCusker, 6 Aaron Shingler, 5 Damian Welch, 4 Sione Timani, 3 Rhys Thomas, 2 Matthew Rees, 1 Iestyn Thomas.
Replacements: 16 Ken Owens, 17 Phil John, 18 Deacon Manu, 19 Kieran Murphy, 20 Jon Edwards, 21 Tavis Knoyle, 22 Stephen Jones, 23 Viliame Iongi.

Munster: 15 Denis Hurley, 14 Johne Murphy, 13 Will Chambers, 12 Lifeimi Mafi, 11 Simon Zebo, 10 Ronan O'Gara, 9 Conor Murray, 8 James Coughlan, 7 Niall Ronan, 6 Peter O'Mahony, 5 Paul O'Connell, 4 Donnacha Ryan, 3 BJ Botha, 2 Damien Varley, 1 Wian du Preez.
Replacements: 16 Denis Fogarty, 17 Marcus Horan, 18 John Hayes, 19 Donncha O'Callaghan, 20 Denis Leamy, 21 Tomas O'Leary, 22 Ian Keatley, 23 Danny Barnes.

Racing 14 London Irish 34

Scorers:

For Racing:
Try: Bobo
Pens: Germain 2
DG: Wisniewski

For London Irish:
Tries: Spratt, Ansbro, Thompstone 2
Cons: Jarvis 4
Pen: Jarvis

Teams:

Racing: 15 Gaetan Germain, 14 Sereli Bobo, 13 Virimi Vakatawa, 12 Josh Matavesi, 11 Juan Imhoff, 10 Juan Martin Hernandez, 9 Mathieu Loree, 8 Jacques Cronje, 7 Bernard Le Roux, 6 Antoine Batut, 5 Jone Qovu Nailiko, 4 Lionel Nallet, 3 Juan Pablo Orlandi, 2 Thomas Bianchin, 1 Julien Brugnaut.
Replacements: 16 Gregory Arganese, 17 Eddy Ben Arous, 18 Johannes Coetzee, 19 Francois van der Merwe, 20 Sebastien Descons, 21 Jonathan Wisniewski, 22 John Leo'o, 23 Sebastien Chabal.

London Irish: 15 Delon Armitage, 14 Topsy Ojo, 13 Joe Ansbro, 12 Jonathan Spratt, 11 Adam Thompstone, 10 Dan Bowden, 9 Darren Allinson, 8 Chris Hala'ufia, 7 Ofisa Treviranus, 6 Declan Danaher, 5 Matthew Garvey, 4 Bryn Evans, 3 Paulica Ion, 2 David Paice, 1 Clarke Dermody.
Replacements: 16 Brian Blaney, 17 Max Lahiff. 18 Faan Rautenbach. 19 Bob Casey, 20 Jamie Gibson, 21 Tom Homer, 22 Adrian Jarvis, 23 Paul Hodgson.