A commemorative coin to mark the engagement of Britain's Prince William and Kate Middleton has been released.

The couple's faces - taken from a photograph at a polo match a few years ago - is etched on the £5 coin which has been approved by the prince, 28, and his grandmother the queen.

Kate is gorgeous but she looks about 60. What were they thinking? While Capital FM DJ Dan Whitehead tweeted: Criticism of Kate Middleton on the new Royal Coin - she does look rough on it.

But critics say despite featuring an engraving of the couple's faces it could be a flop with fans as the etching of Kate's face does not reflect her true beauty.

On the coin, the stunning 28-year-old appears to have a larger nose and dimpled cheeks.

Within hours of the release royal fans started voicing their disproval on social networking site twitter with Wilkielangton writing: "Kate is gorgeous but she looks about 60. What were they thinking?" While Capital FM DJ Dan Whitehead tweeted: "Criticism of Kate Middleton on the new Royal Coin - she does look rough on it."

The coin is available in solid gold for £1,550, as sterling silver plated in gold for £85, and in silver for £55.50.

It comes a few days after official Royal Wedding memorabilia - including a plate, pill box and tankard - was slammed for not featuring the couple's portraits.

Experts said without their image the souvenirs were likely to lose their value in years to come.

One collector told The Sun: "Collectors aren't interested in anything with no portrait. It's not about quality and beauty, anyone in their right mind would prefer something with Kate and Wills on.

"I'm sure they'll shift enough of them but in a couple of years these plates and mugs will be sold on eBay for a fraction of the price."