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It's time for that seasonal debate once again: Are so-called Black Friday bargains all they are cracked up to be?

Research from the consumer group Which? suggests that most products are actually cheaper at other times of year.

But the website Trusted Reviews said that Black Friday can indeed be the best time to buy many products, particularly tech items.

As a result it is advising consumers to download their own price-trackers.

Such trackers can show the history of prices charged, and whether they have been hiked shortly before the promotional period, to make any reduction look larger.

Which goods are cheaper at other times?

Which? tracked the prices of 94 popular products for six months before and after Black Friday last year.

It said that the "overwhelming majority" - some 87% of those goods - were cheaper at other times of year.

Its analysis covered retailers including Currys PC World, Amazon, John Lewis and Argos.

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Most goods came down in price in the six months after Black Friday 2017. For example:

An LG 60 inch TV was advertised at £799 by Amazon on Black Friday. By the end of December it was £150 cheaper

A Sony Cybershot camera was on sale at £189 at Currys PC World on Black Friday. Later it was £10 cheaper

A Fitbit Alta activity tracker was advertised by John Lewis at £99.99 on Black Friday. By March this had been reduced to £39.99

Which goods tend to be cheaper?

Trusted Reviews said it had found many items which had their lowest price on Black Friday 2017. These included:

The Dyson V6 animal wireless vacuum cleaner. It cost £179.99 on Black Friday 2017, its lowest ever price and a 45% reduction

Bose QuietComfort 25 headphones. They cost £159 last Black Friday, a 32% price reduction, and the lowest price until March 2018.

"While amazing deals are available before Black Friday, not every deal is always as good as it seems," said Nick Merritt, editor in chief of Trusted Reviews.

"That's why it's so important people find a trusted source of impartial information before taking the plunge. Doing so could save you hundreds of pounds."

Price-trackers

One way of establishing whether you are getting a bargain or not is to download a price-tracker.

This will give you a full history of how much has been charged for any particular item in the past.

For those who use Google Chrome, Trusted Reviews recommends Keepa, which tracks prices on Amazon. CamelCamelCamel does a similar thing for those who don't use Chrome.

Price Spy tracks prices across hundreds of retailers, including John Lewis and Argos. Idealo claims to track prices across 29,700 different shops in Europe.

Retailer Apps

Another tool for bargain-hunters is a retailer's own app. Many of these will notify consumers when a price of a product has gone down, and by how much.

With a couple of clicks they can then purchase the item.