Keira Knightley says she did not open her letter about being awarded an OBE because she thought it was a demand for tax.
The actress, 33, received the honour at Buckingham Palace earlier this month.
But she tells The Graham Norton Show: “I didn’t open the envelope for about three days.
“It was from the Home Office and it was terrifying because I thought I was in trouble with tax and that I had messed it up and that they were going to take away the house. So, I hid the letter!
“After three days, I thought. ‘I am a mother, I am responsible and I am going to confess to my husband that I’ve messed up.’ So, I opened it and it was a prize!”
Norton’s BBC One show also features actors Guy Pearce, Catherine Tate, Olivia Colman and Nicholas Hoult, as well as singer Rita Ora.
Ora burps the alphabet during the TV show, when asked to demonstrate her New Year’s Eve party piece.
The Graham Norton Show airs on BBC One on Monday December 31 at 10.40pm.