Good acting and outer appearance

I think Keira is up to the challenge, but in this particular case it doesn't really matter, because more than her acting capabilities, what will really have to play a role here, is makeup and wardrobe, and maybe carriage and body language.

More than anything I think it will be the hair and the look.

Maybe they're more alike than we give them credit

It's all about the acting.

Nicole Kidman did a beautiful job playing Virginia Wolf in "The hours" even though they look nothing alike.

Charlize Theron  had a pretty impressive make up job done on her and gained 30 pounds to play Aileen Wuornos in "monster"

Jeffry Write did an awesome job playing Basquit in a film about the  artist's life.

I think it's mainly acting skill and good hair and make up. I don't know how great of an actress Keira Nightly is,  but at least she's got a British accent, so that's a good start...

She's kindof wipsy and her voice is very soft like the Princess.Other than that I don't see any similarities.Keira is a good actress however and I think she'll do the part justice.Cate Blanchett looks nothing like Bob Dylan,but she managed to pull off her portrayel of him in a biopic about his life earlier this year.

Good post,happy holidays!

I think there is no problem with the resemblance as soon as she can portray the character's role, that will be just fine.  Keira is a good actress and I think she will do good in that particular movie. Actually she is one of my favorite

I think that she's a great actress but it would be a plus if they are look-alikes so I think they should try to get another actress that's Diana's look-alike first and use her if there are none. I prefer Nicole Kidman though

I am not sure whether her acting is really at question here, it is whether there should really be a film about Diana when people still feel hurt and have questions