Harlequins took their impressive domestic form on to the European stage as they began their Heineken Cup campaign with yet another win, although this one was in the balance until the final whistle.

And Cardiff Blues kicked off their European Cup campaign in style, beating Racing Metro in Colombes in the other Friday match in the opening round.

The English premiership leaders, Quins, made it 11 victories from 11 attempts this season to spoil Connacht's European Cup debut at the Twickenham Stoop.

The Irish province gave a hugely positive account of themselves after stepping up to the big time following 15 years in the Challenge Cup but Quins did just enough to secure a hard-fought 25-17 triumph in Pool Six.

The reigning Challenge Cup Champions needed two late penalties from the reliable boot of Nick Evans to finally end Connacht's dogged defiance in south west London.

Evans struck his sixth and seventh successful kicks at goal in the 77th and 79th minutes to hand Quins a valuable four match points after Conor O'Shea's side had been outscored by two tries to one.

Evans kicked Quins into a 6-3 led before the game was 10 minutes old but it was Connacht who struck first as far as tries were concerned.

Eoin Griffith's inside step on the edge of the 22 created a two-on-one for the visitors, with Tiernan O'Halloran on hand to claim Connacht's opening Heineken Cup try.

Miah Nikora added the conversion to his seventh-minute penalty and Connacht were 10-6 to the good as the game reached the quarter-of-an-hour mark.

Eric Elwood's men enjoyed plenty of possession and a fair share of territory for the remainder of the half but Quins were the only team to add to their tally before the break.

A third penalty from Evans was followed by a well-taken try from halfback partner Karl Dickson with 31 minutes gone. The former Bedford Blues No.9 burrowed over from close range after Jordan Turner Hall had twice been involved in a patient build up.

Evans completed the seven-point score from wide on the left as he made amends for a penalty miss 10 minutes earlier.

The Kiwi flyhalf then ensured the hosts finished the half two scores clear as Connacht were punished for a high tackle on the ever-industrious Chris Robshaw.

If the Quins faithful expected their side to run away with things in the second period, they were left disappointed, with Connacht ensuring the final 40 minutes were an even tighter affair as they worked their way back to within touching distance of a famous success.

Quins prop and Man of the Match Joe Marler saw a try ruled out for a truck and trailer offence on 49 minutes before Gavin Duffy narrowed the gap with a fine score for Connacht. The Ireland fullback marked another return to his old stomping ground with a 25-metre sprint to the line following a superb cut-out pass from replacement flyhalf Niall O'Connor.

O'Connor calmly slotted the extras to make it a two-point ball game and create an unwanted nervy final quarter as far as the Quins faithful were concerned, but just as the smell of an upset began to surround the Stoop, Evans produced his usual heroics to mark his team's 50th Heineken Cup appearance with what could prove to their most important win of the term so far.

* In the other match on Friday Cardiff kicked off their campaign in style, beating Racing Metro 26-20 in Colombes.

Led by the return of a host of Welsh Internationals the Blues controlled the game for long periods as Racing Metro struggled for a foothold.

The game was marred by an early injury in the second minute to lock James Down who picked up a horrific broken leg at the tackle area and was stretchered from the field before he was replaced by Paul Tito.

It took Cardiff a while to recover from the shock of Down's injury and they found themselves 6-0 down to a penalty by fullback Gaeten Germain and a drop goal by flyhalf Juan Martin Hernandez.

But when the visitors did strike, it led to the game's first try. Tito was tackled into touch just short of the Racing line after a slick handling move but from the line-out, Tongan prop Tau Filise picked up the loose ball for an easy try.

Flyhalf Dan Parks added the conversion to put the visitors a point ahead before the Scot and Germain swapped penalties to give the Cardiff Blues a 10-7 lead midway through the first half.

Racing Metro restored their lead with Argentine Juan Imhoff touching down but just before the break the Blues grabbed their second try with rookie wing Alex Cuthbert scoring in the corner to give the Blues a 17-14 half-time lead.

Parks and Germain swapped penalties during the second period, Parks kicking three to Germain's two as the Welsh region hung on for a deserved victory.

Friday's scorers and scorers!

Racing Métro 20-26 Cardiff Blues

Scorers:

Racing Metro:
Try: Imhoff
Pens: Germain 4
DG: Hernandez

Cardiff Blues:
Tries: Filise, Cuthbert
Cons: Parks 2
Pens: Parks 4

Teams:

Racing Metro: 15 Gaeten Germain, 14 Sereli Bobo, 13 Henry Chavancy, 12 Fabrice Estebanez, 11 Juan Imhoff, 10 Juan Martin Hernandez, 9 Mathieu Loree, 8 Jacques Cronje, 7 Antoine Batut, 6 John Leo'o, 5 Jone Qovu Nailiko, 4 Karim Ghezal, 3 Juan Pablo Orlandi, 2 Benjamin Noirot, 1 Andrea Lo Cicero.
Replacements: 16 Thomas Bianchin, 17 Eddy Ben Arous, 18 Johannes Coetzee, 19 Lionel Nallet, 20 Nicolas Durand, 21 Jonathan Wisniewski, 22 Virimi Vakatawa, 23 Remi Vaquiin.

Cardiff Blues: 15 Chris Czekaj, 14 Alex Cuthbert, 13 Casey Laulala, 12 Jamie Roberts, 11 Tom James, 10 Dan Parks, 9 Lloyd Williams, 8 Xavier Rush, 7 Sam Warburton, 6 Michael Paterson, 5 James Down, 4 Bradley Davies, 3 Taufa'ao Filise, 2 T Rhys Thomas (captain), 1 Gethin Jenkins.
Replacements: 16 Marc Breeze, 17 John Yapp, 18 Scott Andrews, 19 Paul Tito, 20 Andries Pretorius, 21 Richie Rees, 22 Ceri Sweeney, 23 Gavin Evans.

Referee: George Clancy (Ireland)
Assistant referees: John Carvill (Ireland), Brian MacNeice (Ireland)
TMO: Tony Redmond (Ireland)

Harlequins 25-17 Connacht

Scorers:

Harlequins:
Try: Dickson
Con: Evans
Pens: Evans 6

Connacht:
Tries: Duffy, O'Halloran
Cons: O'Connor, Nikora
Pen: Nikora

Teams:

Harlequins: 15 Mike Brown, 14 Seb Stegmann, 13 George Lowe, 12 Jordan Turner-Hall, 11 Sam Smith, 10 Nick Evans, 9 Karl Dickson, 8 Nick Easter, 7 Chris Robshaw, 6 Maurie Fa'asavalu, 5 George Robson, 4 Ollie Kohn, 3 James Johnston, 2 Chris Brooker, 1 Joe Marler. 
Replacements: 16 Joe Gray, 17 Nic Mayhew, 18 Kyle Sinckler, 19 Tomas Vallejos, 20 Luke Wallace, 21 Danny Care. 22 Benjamin Urdapilleta, 23 Tom Williams.

Connacht: 15 Gavin Duffy, 14 Brian Tuohy, 13 Eoin Griffin, 12 Dave McSharry, 11 Tiernan O'Halloran, 10 Miah Nikora, 9 Paul O'Donohoe, 8 George Naoupu, 7 Ray Ofisa, 6 John Muldoon, 5 Mike McCarthy, 4 Michael Swift, 3 Rodney Ah You, 2 Adrian Flavin, 1 Brett Wilkinson.
Replacements: 16 Ethienne Reynecke, 17 Ronan Loughney, 18 Dylan Rogers, 19 Dave Gannon, 20 TJ Anderson, 21 Frank Murphy, 22 Niall O'Connor, 23 Henry Fa'afili.

Referee: Jérôme Garces (France)