This is how to contact the police when you're too scared to speak out loud

You’ve probably played the situation out in your mind at least once – probably many more times – because us human love to catasrophise and use our brains to put ourselves in the worst situations, to work out how we’d react. You’re stuck in some kind of hostage situation, or someone has broken into your home, and you need to get help without anyone realising it.

You can’t call the police, can you, because you’ll have to talk to them on the phone and you’ll get caught. Or at least that’s what a lot of people think. Actually, though, there is a way to warn police that you’re in trouble and need their help without speaking even a single word.

When you call 999, you’re asked if you require police, an ambulance, or the fire brigade. If you say nothing, the operator will ask you to make another noise, such as a cough or a tap on your phone, to let them know you are there.

But say you’re hiding from an attacker and can’t risk making any noise at all, there’s another way to let emergency services know that you are there and that you need them, and haven’t just pocket dialled them by mistake.

If you punch in the number 55, that will alert police to your situation, and then they can trace your phone’s location to get help sent out to you.

Obviously these types of situations are quite prominent in the mind at the moment following the Manchester attack on Sunday night, and Theresa May raising the terror threat to critical, which means that another attack could be “imminent”.

But officials at M15 have stressed that an increased threat level does not mean that members of the public have to do anything other than remain vigilant.

It is also important to remember that the Manchester attack is only the second mass terrorist attack in Britain in the last decade, so events like this are still rare. There are actually far fewer incidents now than there have been in decades.

But still, it’s always good to know what you can do if you find yourself stuck in an awful situation – 55 – remember it and spread the word.