England will go to Cardiff on Saturday relieved to be still hunting a first Grand Slam in a decade after stumbling past a battling Italy.
Six penalties from the boot of Toby Flood dragged his side to victory but this was never the stroll the form book suggested.
England have never lost to Italy in 18 meetings but a well-executed second-half try from Luke McLean and two penalties from Luciano Orquera raised the prospect of a historic upset.
Italy pressed relentlessly in the final 10 minutes as they sought the converted try that would have tied the match, and it took all of England's resolve to keep them at bay.
With four wins from four, Stuart Lancaster's men would have to lose to second-placed Wales by at least seven points to miss out on the Six Nations title.
But this was not the display of Grand Slam champions elect, and a significant improvement will be required if the class of 2013 are to emulate their illustrious predecessors of 2003.
After coming off second best in the scrum in the win over France a fortnight ago, England made a mess of Italy at their first engagement, and Flood stroked over the resultant penalty.
An exchange of penalties did little to enliven a flat atmosphere, and it took a lovely inside pass from Sergio Parisse that almost put Alessandro Zanni in to bring the shivering crowd to voice.
A desperate tackle from Quintin Geldenhuys denied Chris Ashton after an initial Flood break but, for all England's dominance of possession and territory, there was little cutting edge for the first half-hour.
Scrum-half Edoardo Gori was sent to the sin-bin for tackling Flood without the ball after an attempted grubber bounced off the fly-half and threatened to bring the first try, yet England again struggled to capitalise.
Turnover ball and a long floated pass from Alex Goode sent Ashton galloping into space only for the winger to fling the wrong pass inside, and a splendid scything run from Mike Brown left a huge overlap out wide that was again wasted.
Flood's third and fourth penalties for 12-3 at the interval felt like a poor return, another within four minutes of the re-start quickly matched by one from Orquera to make it 15-6.
Against all expectation Italy then struck back with the first try of the match.
A horribly sliced box kick from Danny Care was claimed by Zanni, and when the ball was recycled at pace Orquera's perfectly weighted cross-kick found the unmarked McLean in the left-hand corner.
Had the fly-half nailed the conversion and a subsequent penalty, both from out wide, Italy would have snatched the lead.
Rattled, England reached for their replacements - Ben Youngs coming on for the struggling Care, Joe Marler for Mako Vunipola.
It did little to calm the nascent panic or stem the blue-shirted advance.
Flood's sixth penalty from six extended the lead to seven points but the pressure was all Italy's.
With the minutes ticking away and no sign of any improvement from the home side, Italy launched a series of drives deep into the enemy 22.
Orquera danced and stepped to create half an opening and his forwards pummelled the frantic English rearguard again and again as the visiting fans roared them on.
A knock-on ended that chance but a sliced clearing kick from Flood gave Italy an attacking line-out 10 metres from the line with two minutes left.
A converted try would have finished the Grand Slam talk for good - but replacement Courtney Lawes stole the throw to vast relief from the shivering home support, and England had clung on to set up what will be a fiery denouement in a week's time.
ENGLAND: Goode, Ashton, Tuilagi, Barritt, Brown, Flood, Care, Vunipola, T. Youngs, Cole, Launchbury, Parling, Haskell, Robshaw, Wood.
Replacements: Twelvetrees for Barritt (67), B. Youngs for Care (58), Marler for Vunipola (58), Hartley for T. Youngs (72), Wilson for Cole (76), Lawes for Parling (46), Croft for Haskell (51). Not Used: Burns.
ITALY: Masi, Venditti, G. Canale, Garcia, McLean, Orquera, Gori, De Marchi, Ghiraldini, Castrogiovanni, Geldenhuys, Furno, Zanni, Barbieri, Parisse.
Replacements: Benvenuti for McLean (72), Botes for Gori (58), Lo Cicero for De Marchi (76), Giazzon for Ghiraldini (60), Cittadini for Castrogiovanni (29), Pavanello for Geldenhuys (63), Minto for Furno (63). Not Used: Favaro.
Sin Bin: Gori (30).
Referee: George Clancey (RFU).