England v New Zealand: First ODI, Cardiff
England 291-6 (50 overs): Buttler 72; Ravindra 3-48
New Zealand 297-2 (45.4 overs): Mitchell 118* (91), Conway 111* (121)
New Zealand won by eight wickets
England were beaten by eight wickets as New Zealand comfortably won the opening one-day international in Cardiff.
Set an imposing 292 for victory, unbeaten centuries from Devon Conway (111* off 121 balls) and Daryl Mitchell (118* off 91 balls) saw the Black Caps home with 4.2 overs to spare.
The pair added 180 for the third wicket in a patient run chase on a slow pitch.
All-rounder Ben Stokes made 52 on his return to ODI cricket as England posted 291-6.
Opener Dawid Malan made 54, captain Jos Buttler top-scored with 72 and Liam Livingstone entertained with his 39-ball 52.
Harry Brook, who was drafted into the squad as late batting cover, opened alongside Malan in the absence of Jonny Bairstow and Jason Roy, who missed out through a shoulder injury and back spasm respectively. However, the Yorkshire batter was scratchy for his 25 from 41 balls.
But despite several contributions, none of England's batters were able to kick on in the style of the chanceless Conway, and Mitchell, who made the most of being dropped on 49.
Pace bowler Gus Atkinson, who has been named in England's provisional World Cup squad, made his ODI debut but went wicketless for 47 runs from his seven overs.
The second ODI in the four-match series is in Southampton on Sunday.
England humbled as World Cup preparation continues
The talk around England's World Cup defence has been bubbling, even throughout the drawn T20 series that preceded these ODIs.
And in a repeat of the memorable 2019 final, and what will be England's opening fixture in 27 days' time, it was New Zealand who made a strong statement.
Conway and Mitchell were disciplined throughout, before capitalising late in the innings to target the spin of Adil Rashid and Livingstone to eventually cruise to victory.
Conway struck 13 fours in his knock before launching Livingstone down the ground for the winning runs with a six, and while England did not bowl particularly poorly, they were largely unthreatening.
New Zealand expertly withstood the economical spells of Chris Woakes and David Willey, but England are likely to rotate their bowlers throughout the series with Mark Wood and Sam Curran on the sidelines.
England's World Cup players are not going to feature in the ODIs against Ireland that conclude the summer, which leaves coach Matthew Mott and Buttler with just three more matches to figure out their strongest XI.
And they are no closer to answering the questions that remain, particularly around whether Brook should be included and the make-up of the bowling attack in Indian conditions, after their first outing.
Glimpses of class, but batters fail to capitalise
With four half-centuries, there were promising signs for England's batting line-up, but they lacked the dominant contribution that would have allowed them to post a winning total.
In a makeshift opening partnership in Brook and Malan, it felt like a straight shootout for a World Cup spot - though it remains only speculation that Malan, who is included in the squad, is under pressure.
With an ODI average just shy of 55, he is one of England's most reliable players in the format but perhaps receives criticism because of his more traditional approach, and therefore lower strike-rate, in comparison to some of the line-up.
But he and Brook gave England a solid start with an opening stand of 80 before both fell with no runs added in the space of five balls, and after Joe Root departed for six, left Buttler and Stokes to the rebuild.
They did it efficiently, resorting to a more orthodox style of ODI cricket than England have played in recent years, scoring at five or six an over with minimal risk and punishing the bad ball.
There were glimpses of their brilliance, with a Buttler straight six and Stokes' off-side power, and Livingstone fulfilled his role perfectly with his destructive hitting at the death.
But ultimately, both Mitchell and Conway were ruthless in ensuring their starts were not wasted, from which England's batters should learn.
'Not a major worry for England' - what they said
England captain Jos Buttler on Sky Sports: "It's disappointing. At halfway I thought we actually had a pretty good score.
"Credit to them, it was a fantastic partnership. We couldn't find a way to break that and it opened the game up.
"The way the schedule is, we've got to look after a few guys. It's a quick turnaround so we'll give opportunities and look after guys as well."
Player of the match, New Zealand's Devon Conway on Sky Sports: "I'm pretty happy with the way the innings went. It was nice to get some time in the middle and get the win.
"We thought England's score was just above par, but the bowlers did well to restrict them on that surface. We just knew that if we built those partnerships it would get us over the line."
England bowler James Anderson on BBC Test Match Special: "When Bairstow and Roy are back, they come straight back in, that probably takes out Brook and Livingstone, meaning Moeen to come back in.
"It's not a major worry for England, they've got so much experience in that team. Ben Stokes, Joe Root, these guys love this competition and the big moments."