Amid the continuing controversy about the complications posed by the experimental law variations (ELVs) and the refereeing of the breakdown - and there was plenty of that after this game - the humble knock-on remains one of the game's more straightforward laws. And yet, for all Biarritz's protests about the “one-sided” decision-making at the rucks by Peter Allen, the Scottish referee, a blatant knock-on that he missed was probably the most crucial error of this match on Saturday.

Shortly before half-time, Biarritz overthrew a lineout near their own line. At the tail, Luke Narraway, the Gloucester No8, had only to catch and plunge over, but he failed to hold on to the ball. Several Biarritz players stopped playing, but Gloucester moved the ball swiftly left, where James Simpson-Daniel had acres of space in which to canter over for the score. “When I got the ball, I looked to see whether we were still playing on and I think a few people had that type of reaction,” he said. “But I wasn't going to stop and say, ‘Here you are, have the ball back.'”

Magnus Lund, the Biarritz and former Sale Sharks flanker, who was nearer the scene, said: “The referee told us that it went backwards, but it looked like a knock-on from where I was.”

The score gave Gloucester a 16-3 lead at half-time. They conceded a try shortly after the break, when Romain Cabannes brushed past Olly Barkley to set up Jean-Baptiste Gobelet, but Biarritz's constant difficulties at the breakdown prevented them from generating any sustained pressure.

“We were very, very disappointed with the referee,” Jack Isaac, the Biarritz coach, said. “The refereeing was very one-sided. There were certain things that were blown against us that weren't blown against them. We need to work on a few things and, hopefully, the referees will be working on their game as well.”

In a game that was short of creative sparks, the most intelligent running came from Simpson-Daniel, especially when he moved to outside centre towards the end of the match. Inside him, Barkley was inconsistent, but unquestionably gives Gloucester more options in midfield.

“We play a in very different way to most sides and Olly is just about settling into it,” Dean Ryan, the Gloucester head coach, said.

Scorers: Gloucester: Try: Simpson-Daniel (40+2min). Conversion: Barkley. Penalty goals: Barkley 4 (4, 10, 33, 60). Lamb (80+5). Biarritz: Try: Gobelet (43). Conversion: Peyrelongue. Dropped goal: Peyrelongue (12).

Scoring sequence (Gloucester first): 3-0, 6-0, 6-3, 9-3, 16-3 (half-time), 16-10, 19-10, 22-10.

Gloucester: O Morgan (sin-bin, 22-33); I Balshaw, MTindall, O Barkley (rep: L Vainikolo, 79), JSimpson-Daniel; R Lamb, G Cooper (rep: S Lawson, 59); A Dickinson, O Azam, C Nieto, M Bortolami, ABrown, P Buxton, A Strokosch, L Narraway.

Biarritz: B Thiery (rep: A Masi, 60); T Ngwenya, RCabannes (rep: P Bidabe, 78), D Traille, J-BGobelet; J Peyrelongue, F Cibray; F Barcella (rep: E Coetzee, 69), B August (rep: Barcella, 75), MMoala (rep: B Bourrust, 55), J Thion (sin-bin, 32-41), M Carriza (rep: P Som, 55), M Lund, S Vahafolau, J Cronje.

Referee: P Allen (Scotland).

Attendance: 11,723.