Rebecca Hall has always dreamed of starring in an ''extreme comedy''.

The 36-year-old actress appears alongside comedy duo Will Ferrell and John C. Reilly in 'Holmes & Watson', and she's admitted that starring in the movie is the realisation of a long-held ambition.

Rebecca explained: ''I'm a big believer in trying to do a lot of different genres and different types of things as an actor.

''I think it makes you stronger as an actor. I have really, for a long time, wanted to do some quite extreme comedy, not just more like drama-comedy.''

Rebecca - who previously starred in hits such as 'Vicky Cristina Barcelona' and 'Frost/Nixon' - wears Victorian-era attire in 'Holmes & Watson'.

And the actress has revealed that getting ready for the shoot was a time-consuming process.

She told Screen Rant: ''We're in there are about 24 hours before shooting ... A long time.''

Meanwhile, Rebecca previously admitted to making a ''few personal compromises'' in order to realise her ambitions in the film business.

Reflecting on her career, she explained: ''I don't know how you make a living without a few personal compromises.

''You don't have the opportunity to make the indie film you give a s**t about without making a few of the bigger ones too.

''Of course, there is no way of knowing if a film is going to be good. I've worked on so many films where the script is one thing and then, somewhere down the line - on set, sometimes - it changes and there's zero I can do about it. I'm thinking of one film in particular, but I had better not say.''