Cressida Bonas - the ex-girlfriend of Britain's Prince Harry - is to star in a three-night theatre production.

Cressida Bonas

Cressida Bonas

The 26-year-old actress will play the female lead Cecily Cardew in 'The Importance Of Being Earnest' at the London Oratory.

The show is being put on by Band of Others, a London-based theatre group which is raising money for the Action on Addiction charity.

Cressida's acting career has gathered pace over the last few months, as she has been cast in 'Tulip Fever', which also stars Dame Judi Dench, Christoph Waltz and Cara Delevingne.

However, earlier this month, Cressida confessed she is "paralysingly" shy.

The actress finds it hard to understand why she's short of confidence in her daily life when she's able to perform in front of large crowds.

She said: "I don't really understand it; in real life I'm often so shy - paralysingly so, but when I'm performing, it's totally different. I feel free."

Cressida dated Prince Harry for two years, and the pair were rumoured to have reunited last year, when they were seen attending a London cinema together.

However, Cressida has since thrown herself into her acting, while the prince recently announced plans to quit the Armed Forces.