England survived an almighty scare to finish 36-15 winners at Twickenham as Italy issued a rousing response to scrutiny of their ongoing presence in the Six Nations.
The Grand Slam champions trailed 10-5 at the end of the worst half of Eddie Jones' reign, brought about by their inability to adapt to Italy's crafty refusal to form rucks.
The tactics proved unsettling and a succession of confused senior England players took it in turns to question referee Romain Poite over the ruse, Dylan Hartley making the first enquiry before Owen Farrell, James Haskell and Danny Care also sought answers.
Midway through the first half Haskell produced a comical reply from Poite when asking "how can we get them to form a ruck", to which the French official replied "I can't say, I'm a referee, I'm not a coach".
The discussions with Poite were a constant theme of a first period that ended with Italy wing Giovanbattista Venditti grabbing a penalty attempt that bounced off the left upright and touching down for a try to snatch a scarcely believable lead for the 100-1 underdogs.
Italy's build-up to the match was dominated by debate over whether their decline and the rise of Georgia - who are positioned higher in the world rankings - should see relegation introduced to the Six Nations, but the Azzurri sounded a note of defiance at Twickenham.
Even when England threatened to power clear with tries from Care and Elliot Daly shortly after the interval, Conor O'Shea's men refused to wave the white flag with Michele Campagnaro crossing to set up a tense final quarter.
But their resistance was eventually broken through touch downs from Ben Te'o and Jack Nowell in the last 10 minutes, adding an undeserved gloss to England's 17th successive victory.
Farrell led out the team in recognition of his 50th cap, but it was an uncharacteristically poor afternoon for the world player of the year nominee who completed only four of his six shots at goal.
England were unable to escape their own half for the opening quarter, the sight of Dan Cole conceding two penalties, George Ford kicking straight into touch and Farrell kicking dead reducing Twickenham to an eerie silence.
While the reigning champions were busy shooting themselves in the foot through a flurry of errors - even Farrell looked slightly rattled - Italy were refusing to form rucks, preventing them from being offside.
Italy's dominance would have been reflected by a 6-0 lead on the scoreboard had fly-half Tommaso Allan not missed two routine penalties.
England's first visit to the opposition 22 ended with Cole driving over from an attacking line-out and Italy almost replied in kind only to drop the ball as the whitewash beckoned.
Farrell was lucky to escape punishment for a late shoulder on Edoardo Gori that ended the scrum-half's afternoon and as England's forwards began to generate momentum they coughed up the ball and Italy countered.
Sergio Parisse, Giulio Bisegni and Andries van Schalkwyk swept them over the halfway line and when Nathan Hughes infringed as the hosts scrambled, Allan lined up another penalty shot.
His kick struck the left upright but fortune was smiling on the Azzurri on this occasion and the ball fell into the arms of chasing left wing Venditti and he crashed over.
Allan, who had landed a drop goal shortly before, slotted the conversion to give Italy their scarcely believable interval lead.
But in the space of three minutes after half-time England had powered 17-10 ahead through Care's opportunist try that exploited a lack of concentration from Italy and Daly's sharp finish after strong approach play from Haskell and Te'o.
The floodgates appeared to be opening but Italy soldiered on and when weak tackling from Ford, Daly and Jamie George allowed centre Campagnaro to plunder a soft 61st-minute try, a seismic upset was still possible.
But England found another gear when they needed to with Nowell, Te'o and then Nowell again crossing as Italy tiring defensive line splintered, leaving Jones' men with three wins from three in this season's Six Nations.