Fans of all things comic books may often wish they had the money to spend on some of the gadgets used by some of their favourite superheroes – as Spider-Man, Batman and Superman tackle evil with some of the coolest gizmos around.

But it seems one of the world’s most popular superheroes is willing to let fans in on a little secret about which smartphone he prefers, with Iron Man star Robert Downey Jr signing up to a new lucrative advertising campaign with HTC.

The actor, who has earned millions of fans around the world through his portrayal as billionaire playboy and ingenious engineer Tony Stark, has finalised a two-year contract with the mobile manufacturer.

In what is thought to be the biggest ever deal with HTC, Downey Jr is expected to earn around $12 million (£7.6 million) for his involvement in the campaign.

The move, which will see the Hollywood star promote the company’s new strapline “Here’s to change”, aims to revitalise HTC after its smartphone sales failed to compete with those of rivals Apple and Samsung.

And to mark the launch of the campaign, two online teasers have been released, with the first unsuccessfully attempting to conceal the actor’s identity.

The second was launched yesterday (August 14th) to coincide with Downey Jr’s official unveil as the face of the company and showed the star playing the role of a creative director who was creating different acronyms for the company.

It will also aim to showcase HTC’s new strapline, which is designed to promote the firm’s technical features in an increasingly-saturated mobile market.

Commenting on the deal, HTC’s chief marketing officer Ben Ho said: “With this campaign, we are affirming what HTC’s role is in the mobile market, which is to define change and to lead the industry in developing the newest and most innovative technologies.”

Browse a selection of personalised HTC skins online today.