Wonderful character concept. Have you thought about what kind of athelete he is? Football player or Olympian? It's either one of those or cyclist, rower or curling that the Brits are good at 
Oh there's rugby too, St George is an amateur player - maybe the two superheroes know each other from time spent across the same field?
Also, what are his powers? There is potential for our teams later on in the story to come across/scrap with Germany's superheroes as their teams may come looking to eradicate "Reichson"...
I thought that would be a good plot hook, yes to bring back his past exploits when he was playing for the wrong side as it were.
Reggie is a club Rugby player, obviously very skilled but playing for a relatively minor team (people assume he's waiting for the right offer from one of the big names, or just paying his dues to an old favorite); he did a brief stint as a professional tennis player, was very nearly ranked one of the top 10 players worldwide but dropped out before Wimbledon for undisclosed "health reasons"; He's also a candidate for Britain's olympic team, and could be a real contender for a medal in the 110m hurdle, shotput, long and high jumps, and fencing, if only he'd show up to practice with some regularity.
The experiments performed on him have endowed August with low superhuman physical abilities: augmented strength and agility; enhanced reflexes and alacrity; nigh inexhaustible stamina and improved recuperative abilities; exceptional mental accuity and an expanded mind for learning and language.
Additionally, he has for all appearances aged only a few years since the second world war, and he has remained in near perfect health for that time. Over the years he has picked up expertise in a number of useful fields and studies; particularly advanced genetics and bioengineering; the science which created him and he has done his best to guide the development of. He speaks over a dozen languages, and can read and right in more than a few dead ones; worked as a cryptographer for the KGB, an advanced field instructor for the CIA, and a various other intelligence positions for MI6, Mossad and even as a consultant to the Chinese Secret Service.
Reggie has a lifetime worth of combat experience to draw on, armed and unarmed, close combat and with a variety of firearms, in every climate and environment, and has studied more than a few martial arts. Generally, he favors advanced judo forms and makes excellent and efficient use of various holds and throws, turning his opponents energy and efforts against them.
Under his heroic alias of "Allstar" he makes use of various mundane sports equipment to exceptional effect in incapacitating and disabling his foes, and wears stylised pads in place of armor and what looks like an American Football Helmet to conceal his identity.
While his body stores nutritional reserves at beyond peak efficiency for a human being, August's greatly accelerated metabolic functions give him a propensity to eat and drink to excess whenever opportunity allows; when unable to sustain his increased caloric and nutritional needs, August is forced to 'taper off' his superhuman abilties, or else quickly succumb to an increasing delirium and eventually what appears to be a diabetic coma. Whenever possible, August prefers land and sea travel to air.
