There is no quality control on championships or grand slams.

They record results, not their manner. This result moved Wales a step towards both objectives and was rarely in any doubt. But should they be clinched next week when France form the final obstacle, it is unlikely that this afternoon in the Cardiff sunshine will occupy much time in the commemorative DVDs.

Wales have, though, played with more enterprise than any other team, had injuries to key players yet always found a way to win. As their coach Warren Gatland said while acknowledging the frustrations of the afternoon: "We're still four from four."

This game was predicated on the Welsh plan of getting their powerful wings running at Italy's midfield to try to effect serious damage – which they tested to destruction. As in their win at Twickenham this worked brilliantly in the opening minutes, with George North beating off two tacklers to charge down the middle, but became less and less effective. Italy, who completed 121 tackles, almost double Wales' tally, frequently gave ground but did not break. As Wales wing Alex Cuthbert said: "Their work rate was fantastic."

Wales spent close to 30 of the opening 40 minutes in Italian territory, but had only three penalties from Leigh Halfpenny to one by Mirco Bergamasco to show for their dominance.

But no matter how well organised and committed a defence is, it will tire if forced to work endlessly – and is particularly vulnerable to a turnover. The Welsh breakthrough came 10 minutes after the break as they won possession inside their own half and moved it rapidly to the left. Centre Jamie Roberts received the ball on halfway and angled his line back towards the right to run untouched past Italy's depleted and wrongfooted cover for only his fifth try in 43 games for Wales.

Halfpenny converted and that, for all the galvanic efforts of Italian captain Sergio Parisse, was effectively that. The only question left was how many more points Wales could score.

That it was only eight owed much to Italian defending, as Gatland put it "as if their lives depended upon it" and also to Wales being reduced to 14 men for 10 minutes after Halfpenny took out Parisse in midair.

Outside-half Rhys Priestland added a 69th-minute penalty and Wales' scoring was completed in the 77th minute by the opportunism of captain Gethin Jenkins, whose tap penalty sent Cuthbert on a 50m solo run to the right-hand corner. There was also time for Rhys Webb to make his international debut and during his 10 minutes show the possible benefits to Wales of a scrum-half with quick hands.

Wales: L Halfpenny (J Hook 73); A Cuthbert, J Davies (S Williams 68), J Roberts, G North; R Priestland, M Phillips (R Webb 70), G Jenkins (cap), M Rees (K Owens 62), A Jones (P James 70), A-W Jones (L Charteris 62), I Evans, D Lydiate, T Faletau (R Jones 66), J Tipuric.

Italy: A Masi (G Toniolatti 71), L McLean, G Canale (T Benvenuti 66), A Sgarbi, M Bergamasco, K Burton, F Semenzato (T Botes 66), A Lo Cicero (Cittadini 71), L Ghiraldini (T D'Apice 53), L Cittadini (F Staibano 50), Q Geldenhuys, C van Zyl (M Bortolami 50), A Zanni, S Parisse (cap), S Favaro (S Barbieri 62).

Referee: G Clancy (Ireland).