Organising a wedding involves a ridiculous amount of planning and decision making. When should the big day take place? Who's going to do the catering? Is it better to hire a DJ or a live band? Who is going to train the bride so she knows what to do if she's ever held hostage?

Admittedly, that last one won't apply to most people, but it does to Meghan Markle, whose engagement to Prince Harry means she is set to become one of 2018's new members of the royal family (the other being her unborn niece or nephew).

The former actor is also set to become one of the highest-profile celebrities on the planet, and she needs to be prepared for all that entails.

That means media training, getting used to public engagements and being trained in the art of micro-expressions she can use to convey information in potential hostage videos.

For a high-profile royal – in Markle's case a Duchess come the big day in May 2018 – getting kidnapped ranks among the worst case scenarios.

While it's unlikely to ever happen given the security operation around her, she still needs to be every bit as prepared as her new in-laws.

Scott Jones, director of London-based security firm Garvian, has told TMZ that Markle's training will last about a week and involve learning techniques that allow her to communicate with the outside world through videos, without her captors realising.

This means learning micro-expressions, other signals and using particular keywords to inform her family and security officials whether she's under duress or not.

Her training is also said to include learning how to free herself from restraints such as zip ties and tape. Another source told TMZ her training would be unlikely to include combat or weapons training, and would instead focus on aiding rescue efforts.

Both Kate Middleton and Princess Diana completed similar training.