Imelda Staunton ''felt pretty bad for days'' after shooting a 'Harry Potter' scene where her character dished out a brutal punishment to the titular character.

The 60-year-old actress starred as Ministry of Magic employee Professor Dolores Umbridge, who went on to hold a variety of positions at Hogwarts School of Witchcraft and Wizardry, including Defence Against the Dark Arts teacher and headmistress, in the film saga.

And Imelda admits some of the scenes she had to film as her sinster character were very ''difficult'', particularly one in 'Harry Potter and the Order of the Phoenix' where Harry (Daniel Radcliffe) was forced to write lines - with the words then etching themselves painfully into the back of his hand.

She admitted: ''I want to make sure that I serve the purpose in the story and it was very difficult. I loved doing it, but I have to say, the most difficult scene to do, which did leave me feeling pretty bad for a couple days, was actually the scene where I make him do the lines and it happens in his hand.

''You know, the 'I must not tell lies' detention scene.

''That touched into something that you think, 'Gosh, we're all capable of great cruelty.' It was a horrible, horrible feeling.''

And Imelda found her character's cruelty so hard to take because of her ''absolute and utter belief'' she was doing the right thing.

She added: ''She's not sort of twirling her moustache and saying 'Muahahaha,' it's the absolute and utter belief that actually it is going to help and that's, of course, so much more frightening.''

The British star insists she never felt any ''sympathy'' for her twisted character because she was such a ''monster''.

Speakign to Entertainment Weekly's 'Binge' podcast, she said: ''I don't have to have sympathy at all, not in the slightest,

''I think she's a bloody monster and to be played as such.

''I don't need to understand what she does, but from a character point of view, she believes she's doing the absolute best for that school. Yet again, I have embraced a completely and utterly deluded woman.''