London: Acting legend Dame Maggie Smith is battling breast cancer.

Thesun.co.uk reports that the 73-year-old actress is undergoing radiation therapy but courageously finished filming the latest Harry Potter movie.

"She is dealing with it in her typically brave and understated way. She has had a tumour removed and completed a course of chemotherapy. This was precautionary and the prognosis looks good. The last thing she wants is fuss," said a friend.