Groupon had an offer that sounded too good to be true this morning. A 16GB iPhone 4S for £19. That's apparently a saving of £124.77, or an 87 per cent discount.

Of course to qualify for the deal you have to sign up to a 24-month contract at £34 a month. This includes: Unlimited data including Internet tethering; 5,000 texts per month; 2,000 minutes per month. You also get a Logic3 iPhone Speaker dock according to the description.

According to the Groupon page, 2,546 people have already cashed in on the deal which will run for the next three days.

While the offer is limited to one person, it is possible to 'buy multiples as gifts', which might explain the high number of sales.

The deal is on behalf of, a digital arm of Shebang Technologies Group.

On their website Affordable Mobiles currently offers an iPhone 4S (16GB, black) for free, on a £36 a month contract. This 24-month deal gives users: 300 Minutes; Unlimited Texts; 1.00 Data. The company offers deals from all the major networks.

By comparison, the best iPhone deal (according to MoneySuperMarket) is for a free iPhone 4S, 16GB, 300 minutes, unlimited texts, 500MB data, for £31 a month for 24 months (but including cashback, so it's more like £29.71 a month). That's with Vodafone, via MobilePhonesDirect.

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