People of a certain age will remember the Ask Jeeves search engine and, more importantly, what fun it was to type in rude questions to see what the long-suffering butler might say.

Jeeves may no longer be around, but now everyone with an iPhone or iPad has something similar with Apple's voice assistant, Siri.

Siri has been on hand to help since 2010 and, like Jeeves before her, it's also possible to have a little fun with her .

For example, if you ask Siri to borrow some money, she'll sagely reply with, "Neither a borrower nor a lender be."

Sometimes, however, the harmless Siri fun can stray into something more serious - and potentially harmful.

iPhone users have been taking to Twitter recently telling others to say the number 108 to Siri, adding things like, "You'll thank me later."

Why this is a bad idea.

Saying 108 will in fact put you through to the emergency services in the UK.

This is because 108 is the equivalent of 999 in India, writes The Sun . So what Siri does is recognise it as an emergency call, and puts you through to the services in your area.

You'll be put through the emergency services

Another would-be prankster went one further and urged people to not only say "108", but to then close their eyes for five seconds.

This would of course mean you don't cotton on to the fact you've called the UK's emergency services until it's too late.

Other numbers includes in similar pranks are: 112,110, 000 and the US number 911.

Siri knows to put you through to services in the UK

What makes this prank particularly inadvisable are the thinly stretched resources of our emergency services.

There could also be serious repercussions for anyone caught wasting the emergency services' time.