The Triple Crown holders need unbeaten France to be toppled by either England or Scotland to give them any hope of winning the championship on points difference.

The likelihood of the fallen world champions overcoming Bernard Laportes side have lengthened on the evidence of Saturdays 43-13 mauling at Croke Park.

But OSullivan insists England are capable of registering a shock upset at Twickenham on March 11 as they attempt to haul themselves back into the championship race.

Any team can beat any other on any given day. When France go to Twickenham, all bets are off, said Irelands head coach.

England can put themselves back in the championship with a bang if they beat France.

Theres a lot of motivation for them now and, if they get certain things right, theres no doubt they will beat France.

They wont if they play like they did against us - it doesnt take a rocket scientist to work that out. But I think England will bounce back.

They have a lot to prove. They recognise they did well in the first two games against Scotland and Italy but maybe also now realise they werent tested as much as they thought they had been.

France will test them but England will now have a greater feel for where they are.

It should be very interesting and hopefully theyll blow the Six Nations wide open.

Irelands victory at Croke Park made it four wins in succession against England but O'Sullivan was cautious when asked if the rivals fortunes had undergone a complete reversal since 2003.

The last World Cup year saw England win a Grand Slam, blow New Zealand and Australia away and lift the Webb Ellis trophy.

Now it is Ireland who are being viewed as serious World Cup challengers.

Its great to have won. Weve gone a whole World Cup cycle [four years] without losing to the world champions. That is a good statistic, said OSullivan.

Saturday was a comprehensive victory and the best in that respect. It shows where we are and proves that we are building in the right direction.

You dont get it right every day but, on balance, weve got it right more often than not. This win gives us a lot of confidence.