It was revealed last month that the actress will portray the former prime minister in biopic The Iron Lady. Broadbent will appear alongside Streep as Thatcher's husband Dennis.
"We've started filming," he told the TV Times. "That's why my hair's in a strange white condition."
Praising Streep, he added: "She absolutely captures Maggie. There's only one Meryl."
> Streep's Thatcher to dance with Denis, Reagan