England have recorded 18 successive international victories at this level - including three successive Grand Slams - since 2007, when their annual playing programme was expanded to include summer tours to the Southern Hemisphere.
All but three of the 25-man squad took part in last season's Six Nations victory. The new faces are fly half Henry Slade (Plymouth College & Exeter Chiefs), wing Anthony Watson (St George's Weybridge & London Irish) and lock Tom Jubb (Oaklands College & Saracens).
England beat South Africa 45-13 in Kimberley last summer after tour victories over Boland (36-11) and Western Province (95-0) but the coaching team of John Fletcher and Peter Walton are anticipating a much tougher return trip.
"Age grade form varies from year to year and we had a very good side last year," said Fletcher. "We're sure this year will be a tough tour. France are always good, Namibia will be big and strong and South Africa will be smarting from last year.
"The rugby is important but so is the experience of touring to play against new teams in different environments. We leave on July 12 so it's a tight schedule with a lot of travelling but that all adds to the experience. I like it when the players are under a bit of stress and pressure and it's good to see how they cope and react to it.
"We've got some new players stepping up into the group. Anthony Watson is a wing and full back who was probably the outstanding player in the England Under 16 programme last season. Henry Slade and Tom Jubb both played Under 17 matches for us and did well and all will be available at this level next season."
Five players are unavailable for the trip. Last season's fly half and captain George Ford, No.8 Matt Kvesic and wing Chris Elder will be in pre-season training with the first teams at Leicester Tigers, Worcester Warriors and London Wasps respectively, while London Irish wing Marland Yarde (shoulder) and Harlequins lock Sam Twomey (hand) are injured.
FIXTURES (local times)
July 16: Namibia Invitation XV v England U18 (East London, 11.50am)
July 20: France U18 v England U18 (George, 5pm)
July 23: South Africa U18 v England U18 (Port Elizabeth, 1.25pm)
ENGLAND U18 SQUAD
Nick Auterac (Oaklands College & Saracens)
Dominic Barrow (Prince Henry's GS, Otley & Leeds Carnegie)
Anthony Brennan (Twyford CofE School & London Wasps)
Koree Britton (Ivybridge College & Gloucester Rugby)
Luke Cowan-Dickie (Truro College & Exeter Chiefs)
George Merrick (Whitgift School & Harlequins)
Nathan Moris (Sedbergh School & Newcastle Falcons)
Sam Northcote Green (Dulwich College & London Wasps)
Kyle Sinckler (Epsom College & Harlequins)
Will Skuse (Bryanston School & Bath Rugby)
Will Spencer (St Paul's Catholic & Bath Rugby)
Tom Jubb (Oaklands College & Saracens)
Billy Vunipola (Harrow School & London Wasps)
Chris Walker (Prince Henry's GS, Otley & Leeds Carnegie)
Tommy Bell (Bacup and Rawtenstall GS & Sale Sharks)
Elliot Daly (Whitgift School & London Wasps)
Jamie Elliott (Bedford School & Northampton Saints)
Joel Hodgson (RGS Newcastle & Newcastle Falcons)
Mark Jennings (Lymm HS & Sale Sharks)
Ryan Mills (Hartpury College & Gloucester Rugby)
Ben Ransom (Tonbridge School & Saracens)
Dan Robson (Hartpury College & Gloucester Rugby)
Henry Slade (Plymouth College & Exeter Chiefs)
Charlie Walker (Oakham School & Harlequins)
Anthony Watson (St George's College, Weybridge & London Irish)