Andy Flower has praised the captaincy of Alastair Cook as a crucial factor in England's success in the Investec Ashes. England secured a series win over Australia in Durham on Monday and are now unbeaten in their last 12 Tests and last four series since Cook was appointed.

While Flower, the England team director, admitted the side had not played to their true potential over the first four matches of the series, he was full of praise for the team's attitude and the calm direction provided by Cook.

"I don't think we've played our best cricket in the series," Flower said. "But what we have done is been resilient. We've held ourselves well in pressure situations.

"Cook's captaincy has been excellent: strong in the dressing room and out in the field. He made some decisions that turned the game, such as bringing on Bresnan, who got Warner straight away. He's been maligned in some areas, I've heard. I'm not sure what is said off the field but we judge ourselves by our own standards.

"As a Test captain he is still a young man but he has led the side brilliantly. He's a strong leader and he's made some really good decisions in this Test series."

Cook's leadership has been heavily criticised by some, with former Australian legspinner Shane Warne a persistent negative voice. Indeed, Warne took to Twitter on Monday to say: "Cook is having a horror with his captaincy in the last two Tests. He set the tone early being very defensive and negative today."

Warne was also critical of the decision to bring Bresnan back into the attack on the fourth afternoon of the game. But Bresnan claimed the breakthrough wicket of David Warner with the fourth delivery of a fine six-over spell that also included the wicket of Shane Watson.

Flower also praised the contribution of Stuart Broad, who claimed 11 wickets in the match and produced a top-class spell on the fourth day as England claimed nine wickets after tea. But he admitted the Ashes tour to Australia will present further challenges and require England to adapt.

"It was nice being part of that afternoon session where Broad and Cook turned things around for us," Flower said. "Broad's spell of bowling was outstanding, showing real competitiveness, flair, nous and heart. They are all great qualities that reside in some of these very fine players.

"Playing in Australia will be a bigger challenge and we've already got some of our planning in operation. It will be a tough series and conditions will be very different. South Africa went there last winter and nearly lost to a very similar team to the one we've faced.

"We won in India last winter and that was a good example of adapting to very different conditions. We'll have to do that in Australia if we are to thrive out there."

George Dobell is a senior correspondent at ESPNcricinfo