Facially, it is exhausting, I have to flutter my eyes all the time, which, it turns out, is really knackering! But I think the key to being her is to be completely free – her sexiness came from the fact she was uninhibited. She put across that she did not care how she looked.
In the play Monroe with her co-stars from the 1950s screwball comedy Some Like It Hot are trapped in a purgatory where they have to recreate scenes from the film. It's their penance for having had such an enjoyable life. They have to give other people a good time before they can go to heaven themselves.
It's a role which I've long coveted. During my drama student days my rooms were covered with posters of Marilyn. She still has a massive presence – despite the fact she is dead, she is the biggest sex symbol we have., Her death at 36 – recorded as suicide – continues to draw conspiracy theories.
You'll see her face on bags, or artwork, so she is still really present. And, for me, she is beautiful and intriguing – she is like Elvis in that she had such a fascinating life and maybe, when someone is taken away early, it makes them more interesting.
Monroe famously had close ties with the Kennedy family, including an alleged relationship with the then President, John F Kennedy. It was such an interesting time – you had the Kennedys and the Rat Pack, so it seemed beautiful and glamorous on the surface but delve a little deeper and things become darker.
There were these parties where girls were passed around and the involvement of the Mafia. I think she was murdered. There was no way it was suicide – she had become entwined with Kennedy and she was a loose cannon who became too demanding.
I'm relishing this alter-ego, though I admit I can be brought down with a bump every so often. You think you've nailed the mannerisms and the character – you start to feel like them. Then you catch a glimpse of yourself in the mirror and realise you are not. It can be very disappointing.
Some Like It Hotter is on tour until 27 July playing in Norwich (Playhouse 1-2 July), Borehamwood (The Arc 8-10 July), Bracknell (Wilde Theatre 16-17 July), Worthing (Connaught Theatre 18-20 July) and Guildford (Yvonne Arnaud Theatre 23-27 July).