Robert Downey Jr has starred in a new advertising campaign for HTC, Digital Spy said.

The 48-year-old Iron Man star appears in a series of television ads, which are reportedly costing the company $1 billion.

The actor has signed a two-year deal with HTC, and his first advert for its 'Here to Change' campaign shows the star carrying a briefcase out from a helicopter and walking into a meeting.

It's then that several different slogans and initialisms are revealed to potentially stand for HTC, including Hipster Troll Carwash, Hot Tea Catapult, Hold This Cat and Happy Telephone Company.

A separate video has also been released, showing behind-the-scenes footage from filming the commercial.