Jolie, whose mother died aged 56 after fighting cancer for nearly a decade, said she was speaking out in the hope that other women could benefit from her experience.

^{Brad Pitt and Angelina Jolie (Rex)}

She said her “loving and supportive” partner, the actor Brad Pitt, had been by her side while she underwent three months of operations earlier this year to remove breast tissue and replace it with implants.

The Oscar-winning actress, who has six children with Pitt, three of them adopted, made the difficult decision to have surgery after doctors told her that her faulty gene, known as BRCA1, meant she had an 87 per cent risk of developing breast cancer and a 50 per cent risk of ovarian cancer.

She wrote: “Once I knew that this was my reality, I decided to be proactive and to minimize the risk as much I could. I made a decision to have a preventive double mastectomy.

“I started with the breasts, as my risk of breast cancer is higher than my risk of ovarian cancer, and the surgery is more complex.”

Jolie, whose movies include Lara Croft: Tomb Raider, Mr and Mrs Smith and The Changeling, said waking up after the major operation to remove the breast tissue felt like a “scene out of a science-fiction film”.

^{Hollywood actress Angelina Jolie (Rex/Reuters)}

However, she said the final results of surgery to reconstruct breasts with implants could be “beautiful”. She completed her medical procedures on April 27.

She said: “I wanted to write this to tell other women that the decision to have a mastectomy was not easy.

“But it is one I am very happy that I made. My chances of developing breast cancer have dropped from 87 per cent to under 5 per cent.

“I can tell my children that they don’t need to fear they will lose me to breast cancer. It is reassuring that they see nothing that makes them uncomfortable.

^{In her role as a UNHCR Special Envoy Angelina Jolie recently met Syrian refugees in the Bekaa Valley, Lebanon (EPA)}

“They can see my small scars and that’s it. Everything else is just Mommy, the same as she always was. And they know that I love them and will do anything to be with them as long as I can.

“On a personal note, I do not feel any less of a woman. I feel empowered that I made a strong choice that in no way diminishes my femininity.”

Foreign Secretary William Hague, who in March – during Jolie’s three months of treatment – visited refugee camps in the Democratic Republic of Congo with the actress as part of a campaign to highlight the problem of mass rape in conflict areas, said she was “a brave lady” who would be “an inspiration to many”.

Mr Hague told Sky News: “She is a courageous lady and a very professional lady. She’s done a lot of work with me in recent months.

“She also came over to the G8 foreign ministers’ summit in London to work with me on our initiative on preventing sexual violence in conflict and travelled with me through some difficult places in the Congo.

“She gave no sign that she was undergoing such treatment and I think she’s a very brave lady, not only to carry on with her work so well during such treatment, but also to write about it now and talk about it. I think that she’s a brave lady and will be an inspiration to many.”

Jolie urged other women, in particular those with a family history of breast or ovarian cancer, to seek medical advice so they could make their own informed choice about what steps to take.