Academy Award-winning American actress Meryl Streep will portray the former British Prime Minister in director Phyllida Lloyd's forthcoming biopic.
"I may be persuaded to surrender the hat," Streep is heard saying in the footage. "The pearls, however, are non-negotiable."
Streep previously said of portraying Thatcher: "The prospect of exploring the swathe cut through history by this remarkable woman is a daunting and exciting challenge. I am trying to approach the role with as much zeal, fervour and attention to detail as the real Lady Thatcher possesses - I can only hope my stamina will begin to approach her own!"
Written by Abi Morgan, the film - which will focus on "power and the price that is paid for power" - will also see Jim Broadbent appear as Margaret's husband Denis Thatcher.
Anthony Head, Roger Allam and Richard E Grant are among the supporting cast.
The Iron Lady will open in cinemas on January 6, 2012.