London - New Zealand captain Brendon McCullum expects England to retain the Ashes, saying "they are going to be a tough team to beat".
England begin their defence of the Ashes against arch-rivals Australia in the first of a five-Test series at Trent Bridge, Nottingham, on July 10.
And McCullum is well-placed to assess their standing, having led New Zealand in five Tests, home and away, against Alastair Cook's men this year.
In New Zealand, England had to cling on desperately at the end to square the three-match series 0-0.
But it was a different story in the return series, with England winning a two-Test series 2-0 following a crushing 247-run win in the final Test at Headingley in May.
"I think England are going to be a tough team to beat," said McCullum fafter a washed-out second Twenty20 international at The Oval on Thursday saw New Zealand end their tour with a 1-0 win in a two-match series following a five-run success at the same ground on Tuesday.
"They seem to have got their swagger back against us in that final Test match," McCullum said.
"What we saw in that Test match is a team that when they are firing they are an incredibly tough team, not just to beat but to compete against.
"I thought for long periods of the summer we held our own against them but when it really mattered they flexed their muscles.
"I don't expect that will change in the home summer here against Australia," added McCullum, who also led New Zealand to a 2-1 one-day series win over England during the tour.
In comparison to Australia, who are still coming to terms with the shock axing of their coach Mickey Arthur on Monday, England can so far boast a relatively trouble-free preparation for the Ashes opener.
England have indicated Joe Root will open alongside skipper Cook after national selector Geoff Miller said he was "currently the best opening partner" for the Essex left-hander.
That would mean them doing without the 30-year-old Nick Compton, who scored back-to-back hundreds in New Zealand, but struggled to score 39 runs in four innings during the return series.
Compton, the grandson of England great Denis, made 81 for Somerset in their ongoing tour opener against Australia at Taunton and has been given an unexpected second chance to prove his worth by being released to play for Worcestershire against Australia in the tourists' second and final warm-up match ahead of the first Test.
"It's probably a touch harsh on Compton after scoring two brilliant hundreds against us back home," said McCullum. "For us we came off a Test series where he performed exceptionally well against us.
"We targeted him as one of the key wickets at the top of the order. He pained us for a fair amount of time back home with his innings.
"I thought we bowled exceptionally well to him (in England). They weren't easy batting conditions either at the top of the order."