The Millennium Stadium roof in Cardiff was constructed from 72 steel plane frames, amid 4,500 different components, to assist in keeping out the harshest of conditions. The fear is that that those safeguards may be rendered irrelevant come 5pm on Saturday teatime, as those metal defences struggle to keep out the storm that will inevitably be brewing inside one of world rugby's most vociferous venues.

Higher profile encounters there certainly have been, but few of the 123 previous encounters between Wales and England have had so much riding on them. The Six Nations Championship and the grand slam of course take precedence, but individual performances and the eventual outcome will go someway to dictating the future path for many of the main protagonists.

Warren Gatland, never one to shy away from an opportunity to share the limelight, believes the weekend's crunch fixture will help him decide up to a third of his Lions squad, including who will captain the touring party.

Chris Robshaw remains as captain for England, and while his role at seven is steady, if not cemented for the Lions this summer, his clash with Sam Wurburton will be a telling moment is both players' career. If the Welsh flanker's performance without the captaincy against Scotland is anything to go by, then the decision to see Gethin Jenkins lead the hosts is a shrewd one.

The changes of captain have been one of the few wavering aspects of Wales' three successive away wins. But don't misinterpret those wins following a run of eight defeats as a sign Wales are returning to anything like the form that took them to the grand slam in 2005, 2008 and 2012. The style and verve under Gatland has been replaced by a game based on commitment at the breakdown and the unerring boot of Leigh Halfpenny.

But if Saturday represents anything but Wales's defining moment under interim coach Rob Howley, Stuart Lancaster and his England players know a first grand slam for a decade could be their coming of age ahead of a home World Cup in 2015.

Four wins out of four they may be, but there is still a feeling this England side have much to learn, but that heading to Cardiff they sit on the precipice of defining the remainder of their careers or becoming shrinking violets.

The reality is this group of England players, led by the dominant Robshaw, will become not one nor the other in the Welsh capital, but their state of mind at around 6:40pm could well dictate future success, namely in three years time.

Such are the delicate mathematics, tomorrow's match is a fitting climax to a championship with has offered all the variables of test match rugby. Keeping the roof on things could be difficult.