Angelina Jolie and Brad Pitt determined to ensure help is on hand should the babies put in an early appearance

A military-style set of contingency plans has already been methodically tried and tested.

Last week, for example, the couple and their four children boarded a gold-painted helicopter for a test run to the £2,000-a-night maternity unit of the Princess Grace Hospital in nearby Monaco, where a birthing suite has been reserved.

They have successfully trimmed the trip down to eight minutes door-to-door, and an army-trained pilot has been hired to be on 24-hour standby in case of emergencies.

And in the unlikely event that the weather makes it impossible to fly, Angelina has insisted on a fully functioning Plan B.

So earlier this week, they climbed into a blacked-out, chauffeur-driven Mercedes and, escorted by two SUVs containing their round-the-clock security detail, made the 30-minute drive inland to another private hospital in Grasse.

32-year-old Angelina is already traveling with not only two trained nurses , a midwife, and her own gynaecologist.

Another eminent baby specialist, Dr Jason Rothbart, has agreed to be on hand in Los Angeles to offer advice over the phone to her medical team in France.

But given a host of recent health problems relating to her pregnancy, the Oscar-winning Miss Jolie is adamant that she would rather be safe than sorry.

In no particular order, she has been suffering from painful swollen legs, gestational diabetes and low blood pressure.

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