Six first-half tries helped London Irish survive a second-half fightback to beat Castres 64-27 in the last 16 of the European Challenge Cup.

Ex-France scrum-half Rory Kockott's try then gave the visitors some hope.

Theo Chabouni and Santiago Arata Perrone tries helped make it 40-27, but any thoughts of a stunning upset were dismissed as Irish crossed four times.

Creevy forced his way over after six minutes before Curtis Rona slipped in after Juan Martin Gonzalez's break as Irish went 12-0 ahead after 12 minutes.

Ben Botica's penalty reduced the arrears before Creevy scored his second after 24 minutes.

Irish seemed to be out of sight with three tries in the final six minutes of the half as Tom Pearson, Gozalez and Kyle Rowe got their names on the scoresheet.

Castres scored three tries without reply but when Chabouni was sin-binned for a deliberate knock-on with 10 minutes to go the momentum tipped back Irish's way.

With the French side a man down, Matt Rogerson, Will Joseph, Matt Cornish and Benhard Janse van Rensburg all scored to add gloss to the victory.

Irish will face either Toulon or Benetton in the quarter-finals early next month.

London Irish: Parton; Rowe, Rona, van Rensburg, Hassell-Collins; Jackson, Phipps (capt); Goodrick-Clarke, Creevy, van der Merwe, Coleman, Simmons, Pearson, Gonzalez, O'Brien.

Replacements: Cornish, Gigena, Hoskins, Nott, Rogerson, White, Joseph, Arundell.

Castres: Larregain; Laveau, Aguillon, Botitu, Chabouni; Botica, Kockott (capt); Nostadt, Ngauamo, Tierney, Pieterse, Whetton, Kafatolu, Raisuqe, Ben Nicholas.

Replacements: Humber, Tichit, Guillamon, Jacquet, Kornath, Tukino, Arata, Le Brun.

Referee: Andrea Piardi (Ita).