‘Twas the night before Christmas and all over the country people were looking forward to opening their presents.

There was only one problem; they already had a fairly good idea what their parents or partner had bought them.

Why? Because when you use a tablet or family computer you are likely to notice a stream of adverts for a piece of jewellery, clothing or even cycling equipment that only you would normally be interested in - suggesting someone else has been shopping for those items

Targeted adverts are increasingly revealing secrets about what people have been searching for and buying online, potentially ruining Christmas surprises up and down the land.

The technology behind targeted, or “interest-based”, ads that pop up in banners or on the side of web pages means that when another user goes on the same device - or one that is linked through the same WiFi provider - they are likely to see adverts aimed at the previous user.

That means that if, say, your boyfriend has been browsing for engagement rings, you’ll have a pretty good idea of what’s around the corner.

And if your mother has been searching for that special outfit there’s a good chance it will be under the tree with your name on it.