The Lions raced into an early 10-0 lead but conceded a try on the stroke of half-time to give the Kumuls a sniff and they capitulated in alarming fashion in a dreadful second half as their hosts ran in four tries without reply.
Great Britain, whose brand was revived in eager anticipation after a 12-year absence, struggled to cope with the humidity of Port Moresby and the physical challenge of the Kumuls as they succumbed to only a second defeat by Papua New Guinea.
The result, which followed an opening defeat by a Tongan Invitational XIII and a two-match Test series loss to the Kiwis, piles the pressure on beleaguered head coach Wayne Bennett, whose contract with the Rugby Football League has now expired.
Bennett has spoken of his desire to take England into the 2021 World Cup but it is difficult to see how he can survive such a disastrous tour, culminating in a thrashing by a team containing just two NRL regulars and two who play in the third tier of the English game.
The Lions got off to the worst possible start, losing captain James Graham with a head knock in the very first tackle, which meant an early introduction for Luke Thompson and less impact from the bench.
Yet it was a promising opening quarter from the tourists, with makeshift winger Blake Austin involved in most of the early play and it was the Warrington stand-off who opened the scoring after 14 minutes, taking Jake Connor’s pass to dive over at the corner.
It looked to be plain sailing for Bennett’s men when hooker Josh Hodgson squeezed over for a second try after 21 minutes and Gareth Widdop added the conversion to extend their lead to 10-0.
The scores subdued the passionate capacity crowd at the national stadium but the Kumuls provided a hint of their threat when winger Edene Gebbie went close and they struck in stoppage time when substitute Edwin Ipape scored a breakaway try that turned the game.
Kyle Laybutt’s conversion cut Britain’s lead to just four points and the home side hit the front early in the second half when scrum-half Watson Boas beat Jermaine McGillvary to touch down a grubber kick from Gebbie and captain Rhyse Martin added the goal.
It got even worse for the Lions five minutes later when centre Justin Olam touched down Laybutt’s kick on the last tackle and Martin’s goal made it 18-10.
And there was no way back for Britain when Boas, who plays for League One club Doncaster, re-gathered his own kick to send full-back Alex Johnston over for his side’s fourth try after 56 minutes.
The Lions’ misery was complete when second-rower Nixon Putt pounced on a rare blunder from full-back Jonny Lomax to grab his side’s fifth try after 65 minutes and Martin kicked his third goal.