Barack Obama's election win has heaped pressure on Emma Thompson's unofficially adopted son Tindyebwa Agaba - because his 'mum' now expects him to run for office.

Before Obama's historic victory on November 4, the actress never thought it would be possible for the Rwandan refugee to become a Prime Minister or President - but now she's convinced her 21-year-old student 'son' can make a big difference.

Speaking on Wednesday's Ellen show in America, the British Oscar winner revealed she sees greatness in Agaba's future after taking the former child soldier in when he was 16, and making him part of her family.

She said, "He's just settling in now... He's 21 now, studying social and political science at Exeter University (England), if you please. When Barack got in... my husband was up and woke me... and said, 'It's happened, it's happened'. So I watched his (Obama) speech online and then I texted Tin and I said, 'I expect you to be in office by 2012.'"

The actress has rarely spoken about her 'adopted' son, but told talk show host Ellen Degeneres she and her family bonded with Agaba over Christmas one year.

She explained, "In an organic fashion, he became part of the family. He's a remarkable boy."