Stuart Lancaster has decisions to make ahead of Wales clash... it's time to stick or twist for England coach

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Wales had a surreal insult added to mounting injuries on Monday when they were publicly mocked for their singing ability by Prince William - the vice-patron of their own union.

'I'm just glad you play rugby better than you sing,' quipped the Duke of Cambridge, after Warren Gatland's squad had performed a rendition of the traditional Welsh folk song, Ar Lan y Mor, during their welcome ceremony at London's Guildhall. The royal put-down was perhaps somewhat harsh, but the guests of honour were unfazed - knowing that the real judgment awaits at Twickenham on Saturday, when they lock horns with England.

While it was a bad day for their vocal reputation, for the Welsh there was better news regarding the rather more pressing issue of fitness concerns. As expected, centre Cory Allen was ruled out of the World Cup having torn hamstring soon after scoring a hat-trick of tries against Uruguay - with Tyler Morgan called up to replace him - but the outlook for the other leading casualties is improving.

Warren Gatland (right) shakes Prince William's hand during Wales' Rugby World Cup welcome ceremony

Wales Rugby World Cup squad met Prince William at the London Guildhall on Monday

Prince William light-heartedly mocked Wales' singing ability after they performed Welsh hymn, Ar Lan y Mor

Tighthead prop Samson Lee was moving freely on Monday and should be available to face England, while there is also optimism in the Welsh camp that Liam Williams will be able to continue at full back despite taking a bang to his thigh in the opener on Sunday. Props Paul James and Aaron Jarvis will continue to be assessed in relation to calf and rib cartilage injuries respectively.

'We'll obviously leave it as late as possible with some to see if they recover in time,' said defence coach Shaun Edwards. 'We need to wait for the results of scans. I think there's a couple we feel confident will make it but we can't really make any decisions yet.'

James was wearing a protective boot at the Guildhall and Edwards said: 'He had a kick on his calf and a slight calf strain. I think wearing the boot is just a procedure to help stabilise the foot so there's not much strain on his calf.'

The greatest doubt appears to be Jarvis and if a replacement is required, Rob Evans of the Scarlets is the most likely candidate.

Edwards was more upbeat about Williams' prospects of resuming in the No 15 shirt, adding: 'Liam was pretty sharp in training last week but unfortunately he got a knock during the game so he had to come off. But we're hoping Liam will be fit for Saturday.'

Wales are approaching this game as a decider of sorts. Since the start of Gatland's regime, honours have been even between the neighbouring nations. But there is a sense that Saturday's Welsh visitors to Twickenham relish having their backs to the wall.

Centre Cory Allen has been released from Wales' World Cup squad after suffering a hamstring injury

Allen scored three tries in a 54-9 victory before going off injured and he will miss the rest of the World Cup

Newport Gwent Dragons' Tyler Morgan has replaced Allen in Wales' World Cup squad 

Coach Warren Gatland may be left with a selection headache ahead of his side's trip to face England

'Since 2008 when we came in as the management team, in competitive matches they have won four and we've won four,' said Edwards. 'Even in friendlies, they've won one and we've won one. So it's five-all and it's the rubber match on Saturday. We're the underdogs going into the game, no doubt about it, and we have to bring our competitive edge and spirit.'

While Wales may be forced to consider changes based on medical necessity, England's coaches will weigh up a reshuffle based on the evidence of their hit-and-miss victory over Fiji.

Stuart Lancaster conceded in the aftermath of the tournament opener that his side have to make major improvements and that selection in certain areas would be up for debate.

Powerful cameos by replacements such as Billy Vunipola, Sam Burgess and Joe Launchbury gave food for thought. Wales are alert to the possibility of an altered English line-up being revealed on Thursday, as Edwards said: 'I know their bench had a positive impact and I notice a few comments from the coaches. They will be discussing whether to promote them.'

England head coach Stuart Lancaster (left) watches on as his squad are put through their paces during training

England captain Chris Robshaw (left) was present during their Rugby World Cup training session on Monday 

England's scrum remains a cause for concern, after some trouble in that area against the Fijians. Launchbury would add physical clout to the front five, but Lancaster and his assistants will be wary of demoting Geoff Parling for fear of unsettling the line-out operation.

The equation at No 8 is an ongoing source of intrigue. Ben Morgan was preferred to Billy Vunipola for last Friday's grand occasion and he is showing some shrewd touches around the field.

But the young Saracen gave England momentum when he came on in the second half. Lancaster noted his evident desperation to make a point and that may prove the closest call of all.

England No 8 Billy Vunipola could come in to the starting XV after making an impact as a replacement vs Fiji

Towering lock Joe Launchbury is another who is pushing for a starting berth in Lancaster's XV

Sam Burgess made his presence felt against Fiji too and could start at inside centre for England on Saturday

Burgess emerged from the bench to a rousing reception from the crowd and once again made his presence felt, this time more with his ball-carrying and off-loading than with his trademark tackling ferocity. In fact, he was caught out of position in defence at one stage, but gave the hosts vital purpose going forward and had a hand in Vunipola's bonus-point try.

However, Lancaster and his defence guru, Andy Farrell, will be wary of removing the reassuring influence provided by Brad Barritt, despite his unconvincing contribution to the win over Fiji. His presence as a co-ordinator is valued and allows fly-half George Ford and outside centre Jonathan Joseph to operate as the creative hub around him, but Barritt will not match the fireworks provided by Burgess.

All evidence suggests the England coaches will persist with Barritt, but perhaps they will decide that this is the moment to go for broke.