Iron Man's bulky Hulkbuster suit and a sibling pair of new superheroes in Quicksilver and Scarlet Witch are shown in unpolished "Avengers: Age of Ultron" footage ahead of the San Diego Comic-Con.

After the footage was shown to an exclusive audience in London as part of a promotional event for "Guardians of the Galaxy," UK media listings magazine Radio Times made a record of what was seen on screen.

Tony Stark (Robert Downey Jr.) undergoes a double transformation when he equips his Hulkbuster armor: the get-up is "almost the size of the Hulk himself" and confirms that Iron Man and Hulk are to do battle in the 2015 film.

As far as Quicksilver is concerned, Marvel is taking a risk and will show fans untreated footage, not yet benefiting from the effects work required to turn Aaron Taylor-Johnson into a man of lightning speed.

Quicksilver's sister, Scarlet Witch, is to be played by Elizabeth Olsen, and in comic lore at least her superpowers mean that she can bend statistical probability to her will. In the film, at least for now, this translates to "mysterious reality warping powers" as demonstrated by a psychic block-moving ability -- again, early footage and not necessarily intended for broad consumption.

The pair had both been introduced with cameos in in previous Marvel films, "Captain America Winter Soldier" for Scarlet Witch and "X-Men: Days of Future Past" for Quicksilver (though there played by another actor), while Olsen and Taylor-Johnson both starred in Warner's earlier 2014 hit "Godzilla."

Another part of the reel offered a glimpse of the new Avengers base, built on the site of Tony Stark's old, ruined New York penthouse apartment, with everything a superhero could need, as well as scientific labs for both Stark and the Hulk's nonmonsterous form, Bruce Banner (Mark Ruffalo).

According to the Radio Times, Marvel Studios head Kevin Feige warned the footage "might never be shown again," but US outlets quickly concluded that the montage was a foretaste of what could be shown at the San Diego Comic-Con, an annual event that has become crucial to the "Avengers" franchise and its growing fanbase.

The San Diego Comic-Con is due to take place July 23-27, with the Marvel Studios panel running on the evening of July 26.