England will fly out to Denver this weekend to continue their Rugby World Cup preparations with three Leicester Tigers in a 45-man squad.Tigers trio Dan Cole, Ben Youngs and Tom Youngs are included on the trip, together with Geoff Parling who joined Exeter Chiefs at the end of the domestic season.   Club captain Ed Slater will return to Tigers at the end of the squad’s three-week training camp at Pennyhill but remains on standby, together with Elliot Daly (Wasps), Maro Itoje (Saracens) and Stephen Myler (Northampton Saints).   Nick Easter will remain at Harlequins for treatment on a sore back and will rejoin the squad at Pennyhill Park on August 2 following their post-Denver break.   Ahead of the two-week camp based at Rugby Town USA in Glendale, England head coach Stuart Lancaster said: “Elliot and Maro have fitted in and trained well and it’s been great for them to be in this environment. They are young players who have bright futures. They have made a great impression and I am sure other opportunities will come for them further down the line.   “Steve and Ed, likewise, have contributed greatly. Ed has done well to recover from his knee injury having missed the majority of last season. However, there is a lot of competition in the second row.   “Steve, who is in another really competitive position, has only recently been able to take a full part in training having injured his knee towards the end of last season. But he is getting up to speed and I am sure he would be ready to come back in should the opportunity arise.   "I have spoken to all the players to explain that things can change very quickly and they can come back in at any point.   “The players have worked very hard for the past three weeks and there is a really good feel about the group. Denver is the next stage in our training, a chance to develop further in a different environment.”    England training squad  Chris Ashton (Saracens)  Dave Attwood (Bath Rugby)  Brad Barritt (Saracens)   Kieran Brookes (Newcastle Falcons)  Mike Brown (Harlequins)   Luther Burrell (Northampton Saints)   Sam Burgess (Bath Rugby)  Danny Care (Harlequins)   Danny Cipriani (Sale Sharks)  Calum Clark (Northampton Saints)  Dan Cole (Leicester Tigers)  Alex Corbisiero (Northampton Saints)  Luke Cowan-Dickie (Exeter Chiefs)  Lee Dickson (Northampton Saints)  Kyle Eastmond (Bath Rugby)   Owen Farrell (Saracens)   George Ford (Bath Rugby)   Alex Goode (Saracens)   Jamie George (Saracens)   James Haskell (Wasps)  Jonathan Joseph (Bath Rugby)  Courtney Lawes (Northampton Saints)  Joe Launchbury (Wasps)  George Kruis (Saracens)   Matt Kvesic (Gloucester Rugby)  Joe Marler (Harlequins)   Jonny May (Gloucester Rugby)   Ben Morgan (Gloucester Rugby)  Matt Mullan (Wasps)  Jack Nowell (Exeter Chiefs)   Geoff Parling (Exeter Chiefs)  Chris Robshaw (Harlequins)   Semesa Rokoduguni (Bath Rugby) Henry Slade (Exeter Chiefs)  Billy Twelvetrees (Gloucester Rugby)  Mako Vunipola (Saracens)   Billy Vunipola (Saracens)  Anthony Watson (Bath Rugby)  Rob Webber (Bath Rugby)   Richard Wigglesworth (Saracens)  David Wilson (Bath Rugby)  Tom Wood (Northampton Saints)  Marland Yarde (Harlequins)  Ben Youngs (Leicester Tigers)   Tom Youngs (Leicester Tigers)